Frequency stabilization for a 486nm dye-ring laser

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references (p. 43).For my thesis, I worked towards using two reference cavities to provide frequency stabilization to a 486nm dye-ring laser. After a doubling cavity doubles the frequency to 243nm, the laser beam is used to excite ground state hydrogen to the 2S state: the first step of an experiment to accurately measure the 2S-NS transitions of hydrogen and measure the Lamb shift and Rydberg's constant. Two stabilization cavities were used to prevent the frequency from drifting and to narrow the laser's line-width. I aligned the majority of the optics and coupling light into fiber-optic cables and Fabrey-Perot cavities. Coupling light into a high finesse Fabrey-Perot cavity requires matching the radius of curvature of constant phase of the laser with the geometry of the cavity. To do this, I first measured the physical properties of the laser beam and then numerical arrived at a solution using two lenses to match the conditions imposed by the cavity's geometry. I aligned the cavity and then observed a Pound-Drever-Hall error signal. This error signal will be fed back into the laser to stabilize the frequency. It is anticipated that when the electronics to utilize the error signals are completed, the laser frequency will be stabilized to a hundred hertz, an four order of magnitude improvement over the stability provided by the commericial laser.by Charles A. Sievers.S.B

Generating methane gas from manure (1979)

At first glance, the idea of generating methane gas has considerable merit because it appears to offer at least a partial solution to two pressing problems -- the environmental crisis and the energy shortage. Unfortunately, present-day large-scale methane generation requires rather high investments in money and management which considerably reduce the practicality of the idea for the farmer. This Guide is intended to provide quantitative information so that the feasibility of methane generation can be evaluated for a given situation.Reprinted 5/79/8M

Collecting and preserving waste and wastewater samples for analysis (1993)

Waste handling systems as part of livestock production layouts are being developed and used to protect the environment. One part of waste management is sampling and analyzing the waste and wastewater to know what you have. Information from samples can be valuable for properly operating the system. If results of analyses of waste samples are to be meaningful, then the sample collection and preservation must be done properly. Procedures outlined in this guide are for field sampling from livestock operations. They are not meant as a guide to sampling for scientific research, which in many instances requires specific and highly sophisticated sampling methods

Generating methane gas from manure

At first glance, the idea of generating methane gas has considerable merit because it appears to offer at least a partial solution to two pressing problems -- the environmental crisis and the energy shortage. Unfortunately, present-day large-scale methane generation requires rather high investments in money and management, which considerably reduces the idea's practicality. This guide is intended to provide quantitative information so that the feasibility of methane generation can be evaluated for a given situation.Charles D. Fulhage, Dennis Sievers and James R. Fischer (Department of Agricultural Engineering)Reviewed November 2018 -- websit

Collecting and preserving waste and wastewater samples for analysis

"Waste handling systems as part of livestock production layouts are being developed and used to protect the environment. One part of waste management is sampling and analyzing the waste and wastewater to know what you have. Information from samples can be valuable for properly operating the system. If results of analyses of waste samples are to be meaningful, then the sample collection and preservation must be done properly. Procedures outlined in this guide are for field sampling from livestock operations. They are not meant as a guide to sampling for scientific research, which in many instances requires specific and highly sophisticated sampling methods."--Page 1.Reviewed by David Brune (Department of Agricultural Engineering). Charles D. Fulhage, Jim Porter and Dennis Sievers (Department of Agricultural Engineering

Is the Pre-WMAP CMB Data Self-consistent?

Although individual observational groups vigorously test their data sets for systematic errors, the pre-WMAP CMB observational data set has not yet been collectively tested. Under the assumption that the concordance model is the correct model, we have explored residuals of the observational data with respect to this model to see if any patterns emerge that can be identified with systematic errors. We found no significant trends associated with frequency, frequency channels, calibration source, pointing uncertainty, instrument type, platform and altitude. We did find some evidence at the ~ 1 to ~ 2 sigma level for trends associated with angular scale (l range) and absolute galactic latitude. The slope of the trend in galactic latitude is consistent with low level galactic contamination. The residuals with respect to l may indicate that the concordance model used here needs slight modification. See Griffiths & Lineweaver (2003) for more detail.Comment: 8 pages, 4 figures, to be published in the proceedings of "The Cosmic Microwave Background and its Polarization", New Astronomy Reviews, (eds. S. Hanany and K.A. Olive

Swine waste digester at the University of Missouri--Columbia

Title from JPEG cover page (University of Missouri Digital Library, viewed Feb. 19, 2010)."8/78/3M.

Permutation-adapted complete and independent basis for atomic cluster expansion descriptors

In many recent applications, particularly in the field of atom-centered descriptors for interatomic potentials, tensor products of spherical harmonics have been used to characterize complex atomic environments. When coupled with a radial basis, the atomic cluster expansion (ACE) basis is obtained. However, symmetrization with respect to both rotation and permutation results in an overcomplete set of ACE descriptors with linear dependencies occurring within blocks of functions corresponding to particular generalized Wigner symbols. All practical applications of ACE employ semi-numerical constructions to generate a complete, fully independent basis. While computationally tractable, the resultant basis cannot be expressed analytically, is susceptible to numerical instability, and thus has limited reproducibility. Here we present a procedure for generating explicit analytic expressions for a complete and independent set of ACE descriptors. The procedure uses a coupling scheme that is maximally symmetric w.r.t. permutation of the atoms, exposing the permutational symmetries of the generalized Wigner symbols, and yields a permutation-adapted rotationally and permutationally invariant basis (PA-RPI ACE). Theoretical support for the approach is presented, as well as numerical evidence of completeness and independence. A summary of explicit enumeration of PA-RPI functions up to rank 6 and polynomial degree 32 is provided. The PA-RPI blocks corresponding to particular generalized Wigner symbols may be either larger or smaller than the corresponding blocks in the simpler rotationally invariant basis. Finally, we demonstrate that basis functions of high polynomial degree persist under strong regularization, indicating the importance of not restricting the maximum degree of basis functions in ACE models a priori