Vibration modes of an orbiting radio telescope

Vibration mode shape and frequencies of orbiting radio telescop

The flutter of towed rigid decelerators

Flutter of towed rigid decelerators, and relationships between geometric and aerodynamic parameters defining unconditional stability boundar

A design study for the incorporation of aeroelastic capability into NASTRAN

Modifications and computational tasks required for aeroelastic capability in NASTRA

Spin-axis attitude estimation and magnetometer bias determination for the AMPTE mission

Algorithms were developed for magnetometer biases and spin axis attitude calculation. Numerical examples of the performance of the algorithm are given

The Oxidation of Glucose by Rhizobium meliloti

The extent of oxidation of glucose by Rhizobium meliloti has been determined by comparing the amount of oxygen consumed with the theoretical amount necessary for complete oxidation to carbon dioxide and water. With M/540, M/270, and M/180 concentrations of glucose as a substrate, the rate of oxygen consumption increased rapidly for a period of from 4 to 8 hours then decreased to a low and fairly constant value. The total consumption of oxygen was approximately one-third of the amount required for complete oxidation of the glucose

The flutter of flexible, towed tension shells

Aeroelastic analysis method applied to flutter of flexible, towed tension shel

Mechanics of a coned rotating net

Analysis of deformations, stresses, and vibration modes of rotating net in hypersonic air strea

Linear array of photodiodes to track a human speaker for video recording

Communication and collaboration using stored digital media has garnered more interest by many areas of business, government and education in recent years. This is due primarily to improvements in the quality of cameras and speed of computers. An advantage of digital media is that it can serve as an effective alternative when physical interaction is not possible. Video recordings that allow for viewers to discern a presenter's facial features, lips and hand motions are more effective than videos that do not. To attain this, one must maintain a video capture in which the speaker occupies a significant portion of the captured pixels. However, camera operators are costly, and often do an imperfect job of tracking presenters in unrehearsed situations. This creates motivation for a robust, automated system that directs a video camera to follow a presenter as he or she walks anywhere in the front of a lecture hall or large conference room. Such a system is presented. The system consists of a commercial, off-the-shelf pan/tilt/zoom (PTZ) color video camera, a necklace of infrared LEDs and a linear photodiode array detector. Electronic output from the photodiode array is processed to generate the location of the LED necklace, which is worn by a human speaker. The computer controls the video camera movements to record video of the speaker. The speaker's vertical position and depth are assumed to remain relatively constant– the video camera is sent only panning (horizontal) movement commands. The LED necklace is flashed at 70Hz at a 50% duty cycle to provide noise-filtering capability. The benefit to using a photodiode array versus a standard video camera is its higher frame rate (4kHz vs. 60Hz). The higher frame rate allows for the filtering of infrared noise such as sunlight and indoor lighting–a capability absent from other tracking technologies. The system has been tested in a large lecture hall and is shown to be effective.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98636/1/1742-6596_396_6_062005.pd

Statistical properties of fractures in damaged materials

We introduce a model for the dynamics of mud cracking in the limit of of extremely thin layers. In this model the growth of fracture proceeds by selecting the part of the material with the smallest (quenched) breaking threshold. In addition, weakening affects the area of the sample neighbour to the crack. Due to the simplicity of the model, it is possible to derive some analytical results. In particular, we find that the total time to break down the sample grows with the dimension L of the lattice as L^2 even though the percolating cluster has a non trivial fractal dimension. Furthermore, we obtain a formula for the mean weakening with time of the whole sample.Comment: 5 pages, 4 figures, to be published in Europhysics Letter