Mechanical behavior of irregular fibers part III : the flexural buckling behavior

Fiber buckling behavior is associated with fabric-evoked prickle, which affects clothing comfort and aesthetics. In this paper, the flexural buckling behavior of irregular or nonuniform fibers is studied using the finite element method (FEM). Fiber dimensional irregularities are simulated with sine waves of different magnitude, frequency, and initial phase. The critical buckling loads of the simulated fibers are then calculated from the FE model. The results indicate that increasing the level of irregularity will decrease the critical buckling load of fibers, but the effect of the frequency and initial phase of irregularity on fiber buckling behavior is complicated and is affected by fiber diameter and effective length

Estimation of glottal closure instants in voiced speech using the DYPSA algorithm

Published versio

Low Mass Stars and Brown Dwarfs around Sigma Orionis

We present optical spectroscopy of 71 photometric candidate low-mass members of the cluster associated with Sigma Orionis. Thirty-five of these are found to pass the lithium test and hence are confirmed as true cluster members, covering a mass range of <0.055-0.3M_{sun}, assuming a mean cluster age of <5 Myr. We find evidence for an age spread on the (I, I-J) colour magnitude diagram, members appearing to lie in the range 1-7 Myr. There are, however, a significant fraction of candidates that are non-members, including some previously identified as members based on photometry alone. We see some evidence that the ratio of spectroscopically confirmed members to photometric candidates decreases with brightness and mass. This highlights the importance of spectroscopy in determining the true initial mass-function.Comment: To appear in the 12th Cambridge Workshop on Cool Stars Stellar Systems and the Su

QICS work package 1: migration and trapping of CO2 from a reservoir to the seabed or land surface

Natural CO2 seeps can be used as analogues for studies into surface flux and impact resulting from leaking engineered geological CO2 reservoirs. However their long-lived nature often means that the local environment has either adapted or evolvedaround the seepage site. The ‘Quantifying Impact of carbon storage’ (QICS) experiment provides the solution to this issue by releasing CO2 into an environment previously untouched by CO2. Work Package 1 (WP1) of the QICS project is primarily concerned with the migration of CO2 in the subsurface and how to relate the results of the relatively shallow experiment to a full storage scale setting in the UK North Sea. The main objectives of WP1 are to investigate potential leakage pathways from the reservoir to the surface, determine possible leakage rates and assess the potential volumes of leaked CO2 that can reach the surface environment

Development and accuracy determination of a two-component Doppler Global Velocimeter (DGV)

A two-component Doppler Global Velocimeter (DGV) system was constructed and tested to research problems associated with the accuracy of this unique system. The uniqueness of the system lies in its ability to simultaneously and non-intrusively measure velocities in a laser illuminated plane. A key component of the system is a frequency discriminating optical filter containing iodine vapor which allows direct measurement of the Doppler frequency shift caused by particle motion. Corrections for optical distortions and non-uniform intensities as well as the conversions from intensity data to velocity data are performed by an extensive image processing algorithm. Measurements were made of a 12″ diameter rotating wheel and turbulent pipe/jet flow. Both RMS deviations and velocity range measurement errors from a single component for the rotating wheel with a maximum velocity of 58 m/s were less than 2%, better than most published results, to date, for similar systems. Pipe/jet flow profiles agreed very well with the shape of pitot probe measurements. RMS errors were on the order of 5--10%, but velocity offset error was as much as 10--15% of the 42 m/s velocity range. DGV measured turbulence intensities at the center of the pipe, 4 diameters downstream agreed with hot wire data, with some reservations. Several factors such as repeatability of calibrations, precision of wheel/pipe speed measurement, measurement of viewing angles, and 8-bit camera digitization contributed to the errors in DGV velocity data. Proper techniques for preparing and acquiring correction images are also critical steps toward the goal of producing accurate velocity data