42,055 research outputs found
The Viability of Harvesting Corn Cobs and Stover for Biofuel Production in North Dakota
This study examines the impact of stochastic harvest field time, corn cob and stover harvest technologies, increases in farm size, and alternative tillage practices on profit maximizing potential of corn cob and stover collection in North Dakota. Using three mathematical programming models, we analyze farmers’ harvest activities under 1) corn grain only harvest option, 2) simultaneous corn grain and cob harvest(one-pass) option 3) separate corn grain and stover harvest (two-pass) option. Under the first corn grain only option, farmers are able to complete harvesting corn grain and achieve maximum net income in a fairly short amount of time with existing combine technology. However, under the simultaneous corn grain and cob one-pass harvest option, our findings indicate that farmers generate lower net income as compared to the net income of corn grain only harvest option. This is due to the slowdown in combine harvest capacity as a consequence of attaching cob harvester to the back of combine. Under the third option of a two-pass harvest system, time allocation is the main challenge and our evidence shows that with limited harvest field time available, farmers find it optimal to allocate most of their time harvesting grain, and then proceed to bale stover if time permits at the end of harvest season. As farm size increases, farmers are especially challenged in finding time to harvest both corn grain and cobs/stover. We show that a small decrease in corn yield due to changes in tillage practice can result in a large decline in the net profit of harvesting corn grain and cobs/stover.Cob, Stover, harvest field time, optimization, farm size, tillage, Crop Production/Industries, Production Economics,
Majorana spinors and extended Lorentz symmetry in four-dimensional theory
An extended local Lorentz symmetry in four-dimensional (4D) theory is
considered. A source of this symmetry is a group of general linear
transformations of four-component Majorana spinors GL(4,M) which is isomorphic
to GL(4,R) and is the covering of an extended Lorentz group in a 6D Minkowski
space M(3,3) including superluminal and scaling transformations. Physical
space-time is assumed to be a 4D pseudo-Riemannian manifold. To connect the
extended Lorentz symmetry in the M(3,3) space with the physical space-time, a
fiber bundle over the 4D manifold is introduced with M(3,3) as a typical fiber.
The action is constructed which is invariant with respect to both general 4D
coordinate and local GL(4,M) spinor transformations. The components of the
metric on the 6D fiber are expressed in terms of the 4D pseudo-Riemannian
metric and two extra complex fields: 4D vector and scalar ones. These extra
fields describe in the general case massive particles interacting with an extra
U(1) gauge field and weakly interacting with ordinary particles, i.e.
possessing properties of invisible (dark) matter.Comment: 24 page
Beyond capitalism and liberal democracy: on the relevance of GDH Cole’s sociological critique and alternative
This article argues for a return to the social thought of the often ignored early 20th-century English thinker GDH Cole. The authors contend that Cole combined a sociological critique of capitalism and liberal democracy with a well-developed alternative in his work on guild socialism bearing particular relevance to advanced capitalist societies. Both of these, with their focus on the limitations on ‘free communal service’ in associations and the inability of capitalism to yield emancipation in either production or consumption, are relevant to social theorists looking to understand, critique and contribute to the subversion of neoliberalism. Therefore, the authors suggest that Cole’s associational sociology, and the invitation it provides to think of formations beyond capitalism and liberal democracy, is a timely and valuable resource which should be returned to
Cosmological Constraints from Moments of the Thermal Sunyaev-Zel'dovich Effect
In this paper, we explain how moments of the thermal Sunyaev-Zel'dovich (tSZ)
effect can constrain both cosmological parameters and the astrophysics of the
intracluster medium (ICM). As the tSZ signal is strongly non-Gaussian, higher
moments of tSZ maps contain useful information. We first calculate the
dependence of the tSZ moments on cosmological parameters, finding that higher
moments scale more steeply with sigma_8 and are sourced by more massive galaxy
clusters. Taking advantage of the different dependence of the variance and
skewness on cosmological and astrophysical parameters, we construct a
statistic, ||/^1.4, which cancels much of the dependence on cosmology
(i.e., sigma_8) yet remains sensitive to the astrophysics of intracluster gas
(in particular, to the gas fraction in low-mass clusters). Constraining the ICM
astrophysics using this statistic could break the well-known degeneracy between
cosmology and gas physics in tSZ measurements, allowing for tight constraints
on cosmological parameters. Although detailed simulations will be needed to
fully characterize the accuracy of this technique, we provide a first
application to data from the Atacama Cosmology Telescope and the South Pole
Telescope. We estimate that a Planck-like full-sky tSZ map could achieve a <1%
constraint on sigma_8 and a 1-sigma error on the sum of the neutrino masses
that is comparable to the existing lower bound from oscillation measurements.Comment: 11 pages, 12 figures, to be submitted to Phys. Rev. D; v2: 14 pages,
16 figures, matches PRD accepted version (changes from v1 include additional
calculations with primordial non-Gaussianity and a new appendix discussing
the tSZ kurtosis
In pursuit of the dynamic optimality conjecture
In 1985, Sleator and Tarjan introduced the splay tree, a self-adjusting
binary search tree algorithm. Splay trees were conjectured to perform within a
constant factor as any offline rotation-based search tree algorithm on every
sufficiently long sequence---any binary search tree algorithm that has this
property is said to be dynamically optimal. However, currently neither splay
trees nor any other tree algorithm is known to be dynamically optimal. Here we
survey the progress that has been made in the almost thirty years since the
conjecture was first formulated, and present a binary search tree algorithm
that is dynamically optimal if any binary search tree algorithm is dynamically
optimal.Comment: Preliminary version of paper to appear in the Conference on Space
Efficient Data Structures, Streams and Algorithms to be held in August 2013
in honor of Ian Munro's 66th birthda
Non-Gaussianity and large-scale structure in a two-field inflationary model
Single field inflationary models predict nearly Gaussian initial conditions
and hence a detection of non-Gaussianity would be a signature of the more
complex inflationary scenarios. In this paper we study the effect on the cosmic
microwave background and on large scale structure from primordial
non-Gaussianity in a two-field inflationary model in which both the inflaton
and curvaton contribute to the density perturbations. We show that in addition
to the previously described enhancement of the galaxy bias on large scales,
this setup results in large-scale stochasticity. We provide joint constraints
on the local non-Gaussianity parameter and the ratio
of the amplitude of primordial perturbations due to the inflaton and curvaton
using WMAP and SDSS data
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