1,210 research outputs found
Improved model of the triple system V746 Cas that has a bipolar magnetic field associated with the tertiary
V746 Cas is known to be a triple system composed of a close binary with an
alternatively reported period of either 25.4d or 27.8d and a third component in
a 62000d orbit. The object was also reported to exhibit multiperiodic light
variations with periods from 0.83d to 2.50d, on the basis of which it was
classified as a slowly pulsating B star. Interest in further investigation of
this system was raised by the detection of a variable magnetic field. Analysing
spectra from four instruments, earlier published radial velocities, and several
sets of photometric observations, we arrived at the following conclusions: (1)
The optical spectrum is dominated by the lines of the B-type primary
(Teff1~16500(100) K), contributing 70% of the light in the optical region, and
a slightly cooler B tertiary (Teff3~13620(150) K). The lines of the low-mass
secondary are below our detection threshold; we estimate that it could be a
normal A or F star. (2) We resolved the ambiguity in the value of the inner
binary period and arrived at a linear ephemeris of T_super.conj.=HJD
2443838.78(81)+25.41569(42)xE. (3) The intensity of the magnetic field
undergoes a~sinusoidal variation in phase with one of the known photometric
periods, namely 2.503867(19)d, which we identify with the rotational period of
the tertiary. (4) The second photometric 1.0649524(40)d period is identified
with the rotational period of the B-type primary, but this interpretation is
much less certain and needs further verification. (5) If our interpretation of
photometric periods is confirmed, the classification of the object as a slowly
pulsating B star should be revised. (6) Applying an N-body model to different
types of available observational data, we constrain the orbital inclination of
the inner orbit to ~60 deg to 85 deg even in the absence of eclipses, and
estimate the probable properties of the triple system and its components.Comment: Accepted for publication in Astronomy and Astrophysic
Emerging technologies for sustainable irrigation: Selected papers from the 2015 ASABE and IA irrigation symposium
Citation: Lamm, F. R., Stone, K. C., Dukes, M. D., Howell, T. A., Sr., Robbins, J. W. D., Jr., & Mecham, B. Q. (2016). Emerging technologies for sustainable irrigation: Selected papers from the 2015 ASABE and IA irrigation symposium. Transactions of the Asabe, 59(1), 155-161. doi:10.13031/trans.59.11706This article is an introduction to the "Emerging Technologies in Sustainable Irrigation: A Tribute to the Career of Terry Howell, Sr." Special Collection in this issue of Transactions of the ASABE and the next issue of Applied Engineering in Agriculture, consisting of 16 articles selected from 62 papers and presentations at the joint irrigation symposium of ASABE and the Irrigation Association (IA), which was held in November 2015 in Long Beach, California. The joint cooperation on irrigation symposia between ASABE and IA can be traced back to 1970, and this time period roughly coincides with the career of Dr. Howell. The cooperative symposia have offered an important venue for discussion of emerging technologies that can lead to sustainable irrigation. This most recent symposium is another point on the continuum. The articles in this Special Collection address three major topic areas: evapotranspiration measurement and determination, irrigation systems and their associated technologies, and irrigation scheduling and water management. While these 16 articles are not inclusive of all the important advances in irrigation since 1970, they illustrate that continued progress occurs by combining a recognition of the current status with the postulation of new ideas to advance our understanding of irrigation engineering and science. The global food and water challenges will require continued progress from our portion of the scientific community. This article serves to introduce and provide a brief summary of the Special Collection. © 2016 American Society of Agricultural and Biological Engineers
Diagonally Neighbour Transitive Codes and Frequency Permutation Arrays
Constant composition codes have been proposed as suitable coding schemes to
solve the narrow band and impulse noise problems associated with powerline
communication. In particular, a certain class of constant composition codes
called frequency permutation arrays have been suggested as ideal, in some
sense, for these purposes. In this paper we characterise a family of neighbour
transitive codes in Hamming graphs in which frequency permutation arrays play a
central rode. We also classify all the permutation codes generated by groups in
this family
Using Standardized Evaluation Metrics to Demonstrate Collective Statewide Impacts of Diverse Water Conservation Programming
Although the diversity of Florida Cooperative Extension landscape water conservation programs creates evaluation challenges, it is possible to measure their impacts as a whole. We conducted pilot testing of a statewide evaluation strategy and identified behavior changes resulting in an average monthly water savings of 3,257 gal and utility bill savings of $10.78 per participant. Here we explain the approach we used, providing details about underlying research on water conservation practices and technologies, standardized metrics for demonstrating environmental and economic impacts of behavior/technology adoption, and reporting tools. A focus on statewide impacts based on standardized metrics can be extremely valuable to U.S. Extension professionals
Random tree growth by vertex splitting
We study a model of growing planar tree graphs where in each time step we
separate the tree into two components by splitting a vertex and then connect
the two pieces by inserting a new link between the daughter vertices. This
model generalises the preferential attachment model and Ford's -model
for phylogenetic trees. We develop a mean field theory for the vertex degree
distribution, prove that the mean field theory is exact in some special cases
and check that it agrees with numerical simulations in general. We calculate
various correlation functions and show that the intrinsic Hausdorff dimension
can vary from one to infinity, depending on the parameters of the model.Comment: 47 page
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