Journal Bearings

A plurality of bearing sectors are mounted in a housing. Each sector functions as a lobed area in the bearing to obtain the required lubricant film geometry

Hearing Characteristics and Doppler Shift Compensation in South Indian CF-FM Bats

1. Echolocation pulses, Doppler shift compensation behaviour under laboratory conditions and frequency response characteristics of hearing were recorded inRhinolophus rouxi, Hipposideros speoris andHipposideros bicolor. 2. The frequencies of the constant frequency portions of the CF-FM pulses lie at about 82.8 kHz forR. rouxi from Mahabaleshwar, at 85.2 kHz forR. rouxi from Mysore. Hipposiderid bats have considerably higher frequencies at 135 kHz inH. speoris and 154.5 kHz inH. bicolor. The mean sound durations were 50 ms, 6.4 ms and 4.7 ms, respectively. 3. R. rouxi compensates for Doppler shifts in a range up to typically 4 kHz of positive Doppler shifts (Fig. 2). The Doppler shift compensation behaviour is almost identical to that ofR. ferrumequinum. 4. H. speoris andH. bicolor do not compensate for Doppler shifts under laboratory conditions. Doppler shifts in the echoes induce emission frequency changes which are not correlated to the presented Doppler shifts (Fig. 3). 5. The frequency response characteristics of hearing ofR. rouxi show characteristic sensitivity changes near the bat's reference frequency as also found inR. ferrumequinum. The threshold differences between the low threshold at the reference frequency and a few hundred Hz below are 40 to 50 dB in awake bats (Fig. 5). 6. Frequency sensitivity changes near the emitted CF-frequency of the bats are less pronounced inH. speoris or almost absent inH. bicolor

Echo Delay and Overlap with Emitted Orientation Sounds and Doppler-shift Compensation in the Bat, Rhinolophus ferrumequinum

The compensation of Doppler-shifts by the bat, Rhinolophusferrumequinum, functions only when certain temporal relations between the echo and the emitted orientation sound are given. Three echo configurations were used: a) Original orientation sounds were electronically Doppler-shifted and played back either cut at the beginning (variable delay) or at the end (variable duration) of the echo. b) Artificial constant frequency echoes with variable delay or duration were clamped to the frequency of the emitted orientation sound at different Doppler-shifts. c) The echoes were only partially Doppler-shifted and the Doppler-shifted component began after variable delays or had variable durations. With increasing delay or decreasing duration of the Doppler-shifted echo the compensation amplitude for a sinusoidally modulated + 3 kHz Dopplershift (modulation rate 0.08 Hz) decreases for all stimulus configurations (Figs. 1, 2, 3). The range of the Doppler-shift compensation system is therefore limited by the delay due to acoustic travel time to about 4 m distance between bat and target. In this range the overlap duration of the echo with the emitted orientation sound is always sufficiently long, when compared with data on the orientation pulse length during target approach from Schnitzler (1968) (Fig. 5)

NNNLO correction to the toponium and bottomonium wave-functions at the origin

We report new results of the NNNLO correction to the S-wave quarkonium wave-functions at the origin, which also provide an estimate of the resonance cross section in t-tbar threshold production at the ILC.Comment: 5 pages, 2 figures, Proceedings of 2007 International Linear Collider Workshop: LCWS07 and ILC07, Hamburg, Germany, 30 May - 3 Jun 200

Multiwavelength interferometric observations and modeling of circumstellar disks

We investigate the structure of the innermost region of three circumstellar disks around pre-main sequence stars HD 142666, AS 205 N, and AS 205 S. We determine the inner radii of the dust disks and, in particular, search for transition objects where dust has been depleted and inner disk gaps have formed at radii of a few tenths of AU up to several AU. We performed interferometric observations with IOTA, AMBER, and MIDI in the infrared wavelength ranges 1.6-2.5um and 8-13um with projected baseline lengths between 25m and 102m. The data analysis was based on radiative transfer simulations in 3D models of young stellar objects (YSOs) to reproduce the spectral energy distribution and the interferometric visibilities simultaneously. Accretion effects and disk gaps could be considered in the modeling approach. Results from previous studies restricted the parameter space. The objects of this study were spatially resolved in the infrared wavelength range using the interferometers. Based on these observations, a disk gap could be found for the source HD 142666 that classifies it as transition object. There is a disk hole up to a radius of R_in=0.30AU and a (dust-free) ring between 0.35AU and 0.80AU in the disk of HD 142666. The classification of AS 205 as a system of classical T Tauri stars could be confirmed using the canonical model approach, i. e., there are no hints of disk gaps in our observations.Comment: accepted by Astronomy & Astrophysic