A general purpose wideband optical spatial frequency spectrum analyzer

The light scattered at various angles by a transparent media is studied. An example of these applications is the optical Fourier spectrum measurement resulting from various spatial frequencies which were recorded on a photographic emulsion. A method for obtaining these measurements consists of illuminating the test object with parallel monochromatic light. A stationary lens, placed in the resulting wavefield at a distance of one focal length from the object, will focus parallel waves emanating from the test object at a point lying in the focal plane of the lens. A light detector with a small filtering aperture is then used to measure the intensity variation of the light in the focal or transform plane of the lens. Such measurements require the use of a lens which is highly corrected for all of the common aberrations except chromatic aberration

A microprocessor-based one dimensional optical data processor for spatial frequency analysis

A high degree of accuracy was obtained in measuring the spatial frequency spectrum of known samples using an optical data processor based on a microprocessor, which reliably collected intensity versus angle data. Stray light control, system alignment, and angle measurement problems were addressed and solved. The capabilities of the instrument were extended by the addition of appropriate optics to allow the use of different wavelengths of laser radiation and by increasing the travel limits of the rotating arm to + or - 160 degrees. The acquisition, storage, and plotting of data by the computer permits the researcher a free hand in data manipulation such as subtracting background scattering from a diffraction pattern. Tests conducted to verify the operation of the processor using a 25 mm diameter pinhole, a 39.37 line pairs per mm series of multiple slits, and a microscope slide coated with 1.091 mm diameter polystyrene latex spheres are described

Smallholder Household Maize Production and Marketing Behavior in Zambia: Implications for Policy

CSO/MACO nationally-representative rural surveys provide important insights on smallholder crop marketing behavior from the 2001 and 2004 harvests. Only about 25 percent of smallholder farmers in Zambia sold maize in both seasons, and about 15-20 percent of smallholders sold fresh horticulture as well as groundnuts, with 11-13 percent selling cassava. From 6-10 percent of farmers produced and sold cotton. Overall, Zambian smallholder agriculture has become more diversified over the past decade, with maize, cassava, groundnuts, cotton, horticultural crops, and animal products all becoming important sources of cash revenue as well as production for home consumption (except, of course, cotton). Importantly in both seasons studied, horticulture crop sales are roughly equivalent to the value of maize sales nationwide There is substantial variation in farm income and off-farm income across small farm households, owing to disparities in landholding size, other productive assets, and variables affecting access to markets. Two percent of all smallholder farms nationwide accounted for over 40% of all the maize sold by smallholder households in Zambia in 2000/01 and 2003/04. This same two percent of smallholder households also accounted for about 17% and 20% of the total value of all crop sales of the smallholder sector. Poverty reduction policy options are severely constrained by these production and marketing patterns especially if operating though programs that raise market prices for sellers and buyers.food security, food policy, Zambia, maize, production, marketing, Crop Production/Industries, Q20,

Indoctrination over Objectivity? Examining Breitbart\u27s Framing of Candidates and Social Issues in the 2016 Election

During the 2016 election, Breitbart News became a key conservative source in reporting on the candidates and social issues. Drawing on scholars who have studied news media and politics, this paper uses content analysis to dissect what specific frames appear in Breitbart\u27s coverage. The study finds that Breitbart departs from typical journalistic standards, reinforces problematic gender and racial stereotypes, and utilizes propaganda tactics to spread conservative ideologies. Though it was once considered a fringe source, Breitbart\u27s growing and highly engaged audience demonstrates the platform\u27s potential to shape political discourse and even influence election outcomes

Minimizing Communication in Linear Algebra

In 1981 Hong and Kung proved a lower bound on the amount of communication needed to perform dense, matrix-multiplication using the conventional $O(n^3)$ algorithm, where the input matrices were too large to fit in the small, fast memory. In 2004 Irony, Toledo and Tiskin gave a new proof of this result and extended it to the parallel case. In both cases the lower bound may be expressed as $\Omega$(#arithmetic operations / $\sqrt{M}$), where M is the size of the fast memory (or local memory in the parallel case). Here we generalize these results to a much wider variety of algorithms, including LU factorization, Cholesky factorization, $LDL^T$ factorization, QR factorization, algorithms for eigenvalues and singular values, i.e., essentially all direct methods of linear algebra. The proof works for dense or sparse matrices, and for sequential or parallel algorithms. In addition to lower bounds on the amount of data moved (bandwidth) we get lower bounds on the number of messages required to move it (latency). We illustrate how to extend our lower bound technique to compositions of linear algebra operations (like computing powers of a matrix), to decide whether it is enough to call a sequence of simpler optimal algorithms (like matrix multiplication) to minimize communication, or if we can do better. We give examples of both. We also show how to extend our lower bounds to certain graph theoretic problems. We point out recently designed algorithms for dense LU, Cholesky, QR, eigenvalue and the SVD problems that attain these lower bounds; implementations of LU and QR show large speedups over conventional linear algebra algorithms in standard libraries like LAPACK and ScaLAPACK. Many open problems remain.Comment: 27 pages, 2 table

Is the Glass Half-Empty or Half Full? An Analysis of Agricultural Production Trends in Zambia

One objective of this paper is to examine the trends and changes in crop production before and after the implementation of the partial market liberalization policies starting in the early 1990s. Another objective of the paper is to assess agricultural production performance and its implications for household food security. These issues are examined on the basis of the Crop Forecast Survey (CFS) data, Post Harvest Survey (PHS) data, Central Statistical Office (CSO) price data, data from the Agricultural Market Information Centre (AMIC) at the Ministry of Agriculture, Food and Fisheries (MAFF), and other data.food security, food policy, Zambia, crop production, Crop Production/Industries, Q18,

Is the Glass Half-empty or Half Full? An Analysis of Agricultural Production Trends in Zambia

This policy brief highlights some of the key trends in Zambia agricultural production since the implementation of partial agricultural reform.food security, food policy, Zambia, agricultural production, Farm Management, Q18,

Access to Land and Poverty Reduction in Rural Zambia: Connecting the Policy Issues

Key Policy Message: - Despite having relatively low population densities, inadequate access to land is one of the major causes of rural poverty in Zambia. - The apparent paradox of inadequate access to land for many rural households in a country of low population density is partially reconciled when taking into account that economically viable arable land requires at least some degree of access to basic services, water, road infrastructure, and markets. The basic public investments to make settlement economically viable have yet been made in many areas of Zambia. - Depending of future land allocation policy, access to good quality land with a market potential may become increasingly beyond the reach of many small-scale farm households, making it more difficult to achieve a smallholder-led, pro-poor agricultural development trajectory.zambia, food security, land, policy, Agricultural and Food Policy, Community/Rural/Urban Development, Consumer/Household Economics, Food Security and Poverty, Land Economics/Use, q18, q15,

Analysis of and techniques for adaptive equalization for underwater acoustic communication

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2011Underwater wireless communication is quickly becoming a necessity for applications in ocean science, defense, and homeland security. Acoustics remains the only practical means of accomplishing long-range communication in the ocean. The acoustic communication channel is fraught with difficulties including limited available bandwidth, long delay-spread, time-variability, and Doppler spreading. These difficulties reduce the reliability of the communication system and make high data-rate communication challenging. Adaptive decision feedback equalization is a common method to compensate for distortions introduced by the underwater acoustic channel. Limited work has been done thus far to introduce the physics of the underwater channel into improving and better understanding the operation of a decision feedback equalizer. This thesis examines how to use physical models to improve the reliability and reduce the computational complexity of the decision feedback equalizer. The specific topics covered by this work are: how to handle channel estimation errors for the time varying channel, how to use angular constraints imposed by the environment into an array receiver, what happens when there is a mismatch between the true channel order and the estimated channel order, and why there is a performance difference between the direct adaptation and channel estimation based methods for computing the equalizer coefficients. For each of these topics, algorithms are provided that help create a more robust equalizer with lower computational complexity for the underwater channel.This work would not have been possible without support from the O ce of Naval Research, through a Special Research Award in Acoustics Graduate Fellowship (ONR Grant #N00014-09-1-0540), with additional support from ONR Grant #N00014-05- 10085 and ONR Grant #N00014-07-10184