1,566 research outputs found
The First Comparison Between Swarm-C Accelerometer-Derived Thermospheric Densities and Physical and Empirical Model Estimates
The first systematic comparison between Swarm-C accelerometer-derived
thermospheric density and both empirical and physics-based model results using
multiple model performance metrics is presented. This comparison is performed
at the satellite's high temporal 10-s resolution, which provides a meaningful
evaluation of the models' fidelity for orbit prediction and other space weather
forecasting applications. The comparison against the physical model is
influenced by the specification of the lower atmospheric forcing, the
high-latitude ionospheric plasma convection, and solar activity. Some insights
into the model response to thermosphere-driving mechanisms are obtained through
a machine learning exercise. The results of this analysis show that the
short-timescale variations observed by Swarm-C during periods of high solar and
geomagnetic activity were better captured by the physics-based model than the
empirical models. It is concluded that Swarm-C data agree well with the
climatologies inherent within the models and are, therefore, a useful data set
for further model validation and scientific research.Comment: https://goo.gl/n4QvU
Irrigation Plus Nitrogen Rate Effects on Hybrid Bermudagrass Hay Yield and Quality, With Preliminary Evaluation of NDVI, Tissue, and Soil Nitrate-N Sampling as Diagnostic Tools
A nitrogen fertility study with Vaughn’s hybrid bermudagrass conducted on a Crider silt loam soil (fine, silty, mixed, active, mesic Typic Paleudalfs) over three (3) years (2008-2011) at the Highland Rim Research and Education Center near Springfield, Tennessee is evaluated in this manuscript. Nitrogen applications are evaluated in both irrigated and non-irrigated plots at five (5) different application rates: 0, 56, 112, 168, and 224 kg N ha-1. These rates are applied beginning in late April, and three (3) additional times upon harvests occurring in June, July, and August. Irrigation plots receive enough water to bring total weekly water up to 2.24 cm/plot whenever rainfall is less than that amount. Normalized difference vegetative index (NDVI) measurements are collected mid harvest and on harvest dates to investigate new nitrogen status indicators between Vaughn’s hybrid bermudagrass yields. Plant tissue samples are collected at harvest. Soil samples are collected mid harvest to investigate soil nitrate nitrogen and its relationship with bermudagrass yields.
The results of the study show irrigation has no effect on yields during the period of this study. There is a significant effect resulting from the interaction between month and nitrogen application on yield. Investigation of this interaction reveals two (2) distinct periods of production potential during the growing season. A low to medium yielding period produces an average harvest yield maximum of 3.14 Mg ha-1. A medium to high yield period produces an average harvest yield maximum of 5.4 Mg ha-1. Based on an analysis of variance and mean separation, a nitrogen rate of 56 kg N ha-1 rate is recommended for harvests occurring during the low to medium yielding period, and a nitrogen rate of 113 kg N ha-1 is recommended for those occurring during the high to medium yielding period. NDVI is highly correlated with yield on date of harvest. The results also show NDVI is correlated with mid-harvest yields also, which suggests a possible development of using NDVI as a mid harvest nitrogen status indicator. The results show soil nitrate is not correlated with yield, but did indicate accumulation in the soil as the growing season progressed
Protein Crystal Growth Apparatus for Microgravity
Apparatus for growing protein crystals under microgravity environment includes a plurality of protein growth assemblies stacked one above the other within a canister. Each of the protein growth assemblies includes a tray having a number of spaced apart growth chambers recessed below an upper surface. the growth chambers each having an upstanding pedestal and an annular reservoir about the pedestal for receiving a wick and precipitating agents. A well is recessed below the top of each pedestal to define a protein crystal growth receptacle. A flexible membrane is positioned on the upper surface of each tray and a sealing plate is positioned above each membrane, each sealing plate having a number of bumpers corresponding in number and alignment to the pedestals for forcing the membrane selectively against the upper end of the respective pedestal to seal the reservoir and the receptacle when the sealing plate is forced down
Criminal Homicide in Warren County Kentucky: 1970-1971
Individuals resorting to violent aggression in the form of criminal homicide have often been the object of great public concern. Of the many actions punishable by criminal law, the taking of a human life by another human being most often entails a severe sanction, especially when it has been done deliberately and with a degree of premeditation. Public fear and concern dictate forceful sanctioning toward the homicide offender or offenders; no other criminal offense is so likely to result in the death penalty or life imprisonment
THE IMPLICATIONS OF A NORTH AMERICAN FREE TRADE AREA FOR AGRICULTURE
This is one of two papers commissioned by the International Agricultural Trade Research Consortium on various aspects related to the agricultural sector of a prospective North American Free Trade Agreement. The companion paper to this one has been prepared by a working group chaired by Thomas Grennes, North Carolina State University. To minimize duplication with the Grennes paper, this paper has given greater attention to the general trade policy issues raised by a NAFTA, institutional factors, additional commodity detail in cereals, fruit and vegetables, and the relevance of other regional trade agreements such as the Canada-U.S. Trade Agreement. This work has also benefitted from an earlier report and its annexes, prepared for the Fraser Institute, under the direction of Tim Josling.International Relations/Trade,
Rotor blade construction for circulation control aircraft
A circulation control aircraft rotor blade having a spanwise Coanda surface 16 and a plurality of spanwise extending flexible composite material panels 18 cooperating with the surface to define slots for the discharge of compressed air from within the blade with each panel having first flexure means 60 associated with screw adjustments 36 for establishing a slot opening preload and second flexure means 62 associated with screw adjustments 38 for establishing a slot maximum opening
Neuromechanical Mechanisms of Gait Adaptation in C. elegans: Relative Roles of Neural and Mechanical Coupling
Understanding principles of neurolocomotion requires the synthesis of neural
activity, sensory feedback, and biomechanics. The nematode \textit{C. elegans}
is an ideal model organism for studying locomotion in an integrated
neuromechanical setting because its neural circuit has a well-characterized
modular structure and its undulatory forward swimming gait adapts to the
surrounding fluid with a shorter wavelength in higher viscosity environments.
This adaptive behavior emerges from the neural modules interacting through a
combination of mechanical forces, neuronal coupling, and sensory feedback
mechanisms. However, the relative contributions of these coupling modes to gait
adaptation are not understood. The model consists of repeated neuromechanical
modules that are coupled through the mechanics of the body, short-range
proprioception, and gap-junctions. The model captures the experimentally
observed gait adaptation over a wide range of mechanical parameters, provided
that the muscle response to input from the nervous system is faster than the
body response to changes in internal and external forces. The modularity of the
model allows the use of the theory of weakly coupled oscillators to identify
the relative roles of body mechanics, gap-junctional coupling, and
proprioceptive coupling in coordinating the undulatory gait. The analysis shows
that the wavelength of body undulations is set by the relative strengths of
these three coupling forms. In a low-viscosity fluid environment, the
competition between gap-junctions and proprioception produces a long wavelength
undulation, which is only achieved in the model with sufficiently strong
gap-junctional coupling.The experimentally observed decrease in wavelength in
response to increasing fluid viscosity is the result of an increase in the
relative strength of mechanical coupling, which promotes a short wavelength.Comment: Pages 25, Figures 14. Submitted to SIAM Journal on Applied Dynamical
System
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