11,723 research outputs found
A.E.S. Circular, No. 39
During 1979 and 1980, soil fertility research was conducted at two locations in the Delta
Clearwater area. One of the test sites, Lee F ett’s Farm, was cleared in the mid-1950s and has been in production for about 25 years. The other test site is situated on a tract of newly cleared
land owned by Dennis Green. The new lands site was cleared by the traditional berm-pile method during the winter of 1978-79. This method removes much of the moss layer, and in some cases,
part o f the topsoil. Land cleared by this procedure is lower in natural fertility, but has the advantage
of enabling the farmer to plant a crop the first summer after clearing.
In this publication, progress reports are given for several research projects involving fertilizer use and rates of application.Introduction -- Weather Summary for the 1979 and 1980 Growing Season: Table 1: Climatic Data for Delta Junction During the 1979 and 1980 Growing Season -- Response of Barley to Nitrogen and Phosphorus Fertilizer Applications on New Land:
Table 2: Response of Barley to Nitrogen and Phosphorus Fertilizers on New Land
in the Delta-Clearwater Area of Alaska -- Variety-Fertilizer Interactions of Barley Grown on Newly Cleared Land: Table 3: Variety-Fertilizer Interactions of Barley Grown on New Land in the Delta-Clearwater Area of Alaska -- Response of Barley and Rapeseed to Sulfur Fertilization: Table 4: Response of Barley to Sulfur Fertilization When Grown Under
Different Crop Rotations; Table 5: Response of Sulfur Fertilization When Grown Under Different Crop Rotation
POLICY ALTERNATIVES TO REDUCE BARRIERS AFFECTING ACCESS TO RESOURCES FOR OWNERS OF SMALL FARMS IN RURAL AREAS
Agricultural and Food Policy,
An innovative approach to compensator design
The design is considered of a computer-aided-compensator for a control system from a frequency domain point of view. The design technique developed is based on describing the open loop frequency response by n discrete frequency points which result in n functions of the compensator coefficients. Several of these functions are chosen so that the system specifications are properly portrayed; then mathematical programming is used to improve all of these functions which have values below minimum standards. To do this, several definitions in regard to measuring the performance of a system in the frequency domain are given, e.g., relative stability, relative attenuation, proper phasing, etc. Next, theorems which govern the number of compensator coefficients necessary to make improvements in a certain number of functions are proved. After this a mathematical programming tool for aiding in the solution of the problem is developed. This tool is called the constraint improvement algorithm. Then for applying the constraint improvement algorithm generalized, gradients for the constraints are derived. Finally, the necessary theory is incorporated in a Computer program called CIP (compensator Improvement Program). The practical usefulness of CIP is demonstrated by two large system examples
On the Minimum Distance of Generalized Spatially Coupled LDPC Codes
Families of generalized spatially-coupled low-density parity-check (GSC-LDPC)
code ensembles can be formed by terminating protograph-based generalized LDPC
convolutional (GLDPCC) codes. It has previously been shown that ensembles of
GSC-LDPC codes constructed from a protograph have better iterative decoding
thresholds than their block code counterparts, and that, for large termination
lengths, their thresholds coincide with the maximum a-posteriori (MAP) decoding
threshold of the underlying generalized LDPC block code ensemble. Here we show
that, in addition to their excellent iterative decoding thresholds, ensembles
of GSC-LDPC codes are asymptotically good and have large minimum distance
growth rates.Comment: Submitted to the IEEE International Symposium on Information Theory
201
Spatially Coupled LDPC Codes Constructed from Protographs
In this paper, we construct protograph-based spatially coupled low-density
parity-check (SC-LDPC) codes by coupling together a series of L disjoint, or
uncoupled, LDPC code Tanner graphs into a single coupled chain. By varying L,
we obtain a flexible family of code ensembles with varying rates and frame
lengths that can share the same encoding and decoding architecture for
arbitrary L. We demonstrate that the resulting codes combine the best features
of optimized irregular and regular codes in one design: capacity approaching
iterative belief propagation (BP) decoding thresholds and linear growth of
minimum distance with block length. In particular, we show that, for
sufficiently large L, the BP thresholds on both the binary erasure channel
(BEC) and the binary-input additive white Gaussian noise channel (AWGNC)
saturate to a particular value significantly better than the BP decoding
threshold and numerically indistinguishable from the optimal maximum
a-posteriori (MAP) decoding threshold of the uncoupled LDPC code. When all
variable nodes in the coupled chain have degree greater than two,
asymptotically the error probability converges at least doubly exponentially
with decoding iterations and we obtain sequences of asymptotically good LDPC
codes with fast convergence rates and BP thresholds close to the Shannon limit.
Further, the gap to capacity decreases as the density of the graph increases,
opening up a new way to construct capacity achieving codes on memoryless
binary-input symmetric-output (MBS) channels with low-complexity BP decoding.Comment: Submitted to the IEEE Transactions on Information Theor
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