Class-D audio amplifiers with negative feedback

There are many different designs for audio amplifiers. Class-D, or switching, amplifiers generate their output signal in the form of a high-frequency square wave of variable duty cycle (ratio of on time to off time). The square-wave nature of the output allows a particularly efficient output stage, with minimal losses. The output is ultimately filtered to remove components of the spectrum above the audio range. Mathematical models are derived here for a variety of related class-D amplifier designs that use negative feedback. These models use an asymptotic expansion in powers of a small parameter related to the ratio of typical audio frequencies to the switching frequency to develop a power series for the output component in the audio spectrum. These models confirm that there is a form of distortion intrinsic to such amplifier designs. The models also explain why two approaches used commercially succeed in largely eliminating this distortion; a new means of overcoming the intrinsic distortion is revealed by the analysis. Copyright (2006) Society for Industrial and Applied Mathematic

Tracking errors and optical scatter in a solar tracker with linear regression error correction

March 1998.Also issued as Norman Bryce Wood's thesis (M.S.) -- Colorado State University, 1998.Includes bibliographical references.Tracking errors were assessed for a computer controlled solar tracker. The effects of optical scattering on radiometric measurements performed with the tracker were also evaluated. As the position of the tracker is iteratively corrected over time, linear regression is used to calculate a best-fit correction for tracking error. The performance of the tracker was found to be sensitive to the timing of the iterative corrections and to the errors associated with those corrections. Using an optimized scheme for iterative corrections in a field test, the average tracking error was found to be 0.11 ± 0.05 degrees for 48 hours following the final iterative correction. The solar tracker may be fitted with a mirror which can reflect the image of a target into an instrument. Because the mirror is exposed to multiple sources of illumination (direct sunlight, skylight, and light from surrounding objects) the scattering properties of the mirror are important. The intensity of light scattered from the mirror was compared with the intensity of diffuse skylight. Scatter from the diffuse field incident on the mirror (background scatter) was found to be more significant than scatter from the direct solar beam, and both were significant compared to the intensity of diffuse skylight. Background scatter ranged from 20% to 70% of the total measured signal, depending on scattering geometry and wavelength. Solar scatter ranged from 1% to 20%, also depending on scattering geometry and wavelength. The scattering properties of the mirror, as measured by the bidirectional reflectance distribution function, appeared to be anisotropic, possibly because of surface defects. For the wavelengths examined, the scattering properties did not follow the wavelength scaling law predicted by Rayleigh-Rice theory for clean, smooth, front-surface reflectors.Sponsored by the National Aeronautics and Space Administration (grant no. NAG1-1704); the Office of Naval Research (contract no. N00014-91-J-1422); and the Department of Defense Center for Geoscience Phase II (contract no. DAAH04-94-G-0420)

Inference of stratospheric temperature and water-vapor structure from limb radiance profiles

February 1972.Includes bibliographical references

A mixer design for the pigtail braid

The stirring of a body of viscous fluid using multiple stirring rods is known to be particularly effective when the rods trace out a path corresponding to a nontrivial mathematical braid. The optimal braid is the so-called "pigtail braid", in which three stirring rods execute the usual "over-under" motion associated with braiding plaiting) hair. We show how to achieve this optimal braiding motion straightforwardly: one stirring rod is driven in a figure-of-eight motion, while the other two rods are baffles, which rotate episodically about their common centre. We also explore the extent to which the physical baffles may be replaced by flow structures (such as periodic islands)

Analysis of tethered balloon, ceilometer and class sounding data taken on San Nicolas Island during the FIRE project

During the FIRE Marine Stratocumulus Program on San Nicolas Island, Colorado State University (CSU) and the British Meteorological Office (BMO) operated separate instrument packages on the NASA tethered balloon. The CSU package contained instrumentation for the measurement of temperature, pressure, humidity, cloud droplet concentration, and long and short wave radiation. Eight research flights, performed between July 7 and July 14, are summarized. An analysis priority to the July 7, 8 and 11 flights was assigned for the purposes of comparing the CSU and BMO data. Results are presented. In addition, CSU operated a laser ceilometer for the determination of cloud base, and a CLASS radiosonde site which launched 69 sondes. Data from all of the above systems are being analyzed

Improved solar tracking system with linear regression error correction

July 1996.Includes bibliographical references.A motor driven two-axis optical mount combined with PC-based solar position and correction software is easily set up and provides highly accurate tracking of the sun. During setup, the tracker needs only to be approximately aligned, then a series of simple, manual corrections can be made which lead to automatic correction for misalignment. With accurate manual corrections, the tracking accuracy can approach 0.1 degrees. Various tracking options allow the user to scan repeatedly across the solar disc, track a position offset from the sun, or reflect the solar image into another instrument. The system includes a two-axis mount driven by servo motors with optical encoder position indication; servo amplifiers; a personal computer equipped with a two-axis motor controller; software for calculating solar position; and error correction software. The optical encoders have a resolution of 0.1 arcseconds per step, and the solar position software agrees to within 1.25 arcminutes with U.S. Naval Observatory calculations of solar position. The error correction software applies linear regression via singular value decomposition to a series of manual tracking corrections. The regression creates a best-fit compensation for misalignment of the mount. Several factors are evaluated for their influence on tracker performance. These factors include the initial misalignment of the tracker, errors in the manual corrections, and the frequency of the manual corrections. Performance is largely insensitive to the magnitude and orientation of the initial misalignment, but sensitive to the accuracy and frequency of manual corrections. Based on this sensitivity, a manual correction scheme is developed which improves the performance of the correction software. The performance of the tracker, employing the correction scheme, is evaluated using both a computer simulation of the tracker and field testing. Computer tests with simulated random manual correction errors show that the correction algorithm can achieve accuracy within two times the standard deviation of the correction errors. This accuracy is maintained following final manual correction for test periods as long as 54 hours. In the field test, highly accurate manual corrections were made by reflecting the solar image to a wall about 100 feet from the tracker. The observed tracking errors are 0.11 +/- 0.05 degrees for 48 hours following the final manual corrections.Sponsored by the National Aeronautics and Space Administration contract no. NAG 1-1704, and the Office of Naval Research contract no. N00014-91-J-1422, P00007

Laboratory investigation of radiative transfer in cloud fields, A

April 1978.Includes bibliographical references (page 46).Sponsored by the Global Atmospheric Research Program, National Science Foundation, and the GATE Project Office, National Oceanic and Atmospheric Administration ATM-77-15369.Sponsored by the Global Atmospheric Research Program, National Science Foundation, and the GATE Project Office, National Oceanic and Atmospheric Administration OCD-74-21678

Influence of wet distillers grains diets on beef cattle fecal bacterial community structure

<p>Abstract</p> <p>Background</p> <p>The high demand for ethanol in the U.S. has generated large stocks of wet distillers grains (DG), a byproduct from the manufacture of ethanol from corn and sorghum grains. Little is known, however, about the potential influence of dietary DG on fecal microbial community structure. A better understanding of the microbial population in beef cattle feces could be an important monitoring tool to facilitate goals of improving nutrient management, increasing animal growth performance and decreasing odors and/or shedding of pathogens. Five diets consisting of a traditional diet fed to finishing beef cattle in the Southern High Plains of Texas-CON (steam-flaked corn control with 0% DG), and four concentrations of DG in the dietary dry matter; 10 C (10% corn-based DG), 5S (5% sorghum-based DG), 10S (10% sorghum DG), and 15S (15% sorghum DG) were fed to steers at the Texas Tech University Burnett Animal Center. Diets were essentially isonitrogenous with a formulated crude protein value of 13.5%.</p> <p>Results</p> <p>Fecal grab samples were obtained from 20 steers (n = 4 per diet) and the barcoded DNA pyrosequencing method was used to generate 127,530 16S operational taxonomic units (OTUs). A total of 24 phyla were observed, distributed amongst all beef cattle on all diets, revealing considerable animal to animal variation, however only six phyla (core set) were observed in all animals regardless of dietary treatment. The average abundance and range of abundance, respectively of the core phyla were as follows: Firmicutes (61%, 19 to 83%), Bacteroidetes (28%, 11 to 63%), Proteobacteria (3%, 0.34 to 17.5%), Tenericutes (0.15%, 0.0 to 0.35%), Nitrospirae (0.11%, 0.03 to 0.22%), and Fusobacteria (0.086%, 0.017 to 0.38%). Feeding DG-based diets resulted in significant shifts in the fecal microbial community structure compared with the traditional CON. Four low abundance phyla significantly responded to dietary treatments: Synergistetes (<it>p </it>= 0.01), WS3 (<it>p </it>= 0.054), Actinobacteria (<it>p </it>= 0.06), and Spirochaetes (<it>p </it>= 0.06).</p> <p>Conclusions</p> <p>This is, to our knowledge, the first study using this method to survey the fecal microbiome of beef cattle fed various concentrations of wet DG. Comparison of our results with other cattle DNA sequencing studies of beef and dairy cattle feces from a variety of geographical locations and different management practices identifies a core set of three phyla shared across all cattle. These three phyla, in order of relative abundance are; Firmicutes, Bacteroidetes, and Proteobacteria. The presence of large animal-to-animal variation in cattle microbiome was noted in our study as well as by others.</p

Self-Calibration of Cameras with Euclidean Image Plane in Case of Two Views and Known Relative Rotation Angle

The internal calibration of a pinhole camera is given by five parameters that are combined into an upper-triangular $3\times 3$ calibration matrix. If the skew parameter is zero and the aspect ratio is equal to one, then the camera is said to have Euclidean image plane. In this paper, we propose a non-iterative self-calibration algorithm for a camera with Euclidean image plane in case the remaining three internal parameters --- the focal length and the principal point coordinates --- are fixed but unknown. The algorithm requires a set of $N \geq 7$ point correspondences in two views and also the measured relative rotation angle between the views. We show that the problem generically has six solutions (including complex ones). The algorithm has been implemented and tested both on synthetic data and on publicly available real dataset. The experiments demonstrate that the method is correct, numerically stable and robust.Comment: 13 pages, 7 eps-figure