198,002 research outputs found
Nuclei in the Cosmos III Third International Symposium on Nuclear Astrophysics
No full textproceedings book (615 pages) of the Nuclei in the Cosmos n. III symposium held in Assergi, L'Aquila, in 1994. M. Busso is the chairman of the organizing commitee and the first edito
Commuting Zones in Mexico
No full textThis dataset contains a definition of commuting zones in Mexico as described in Blyde, J., M. Busso, and D. Romero (2020) "Labor Market Adjustment to Import Competition: Long-Run Evidence from Establishment Data", IDB Working Paper Series 1100, http://dx.doi.org/10.18235/000214
The puzzle of silicon, titanium, and magnesium anomalies in meteoritic silicon carbide grains
No full textAn astrophysical interpretation of the silicon, titanium, and magnesium
isotope anomalies measured in the mainstream population of single
silicon carbide (SiC) grains extracted from carbonaceous meteorites is
presented. The condensation site of the grains is envisaged in the cool
atmospheres of carbon stars. The Si isotope anomalies show a general
linear correlation between Si-29/Si-28 aand Si-30/Si-28, whose slope
cannot be explained only by s-processing in the He-burning shell and
dilution with material of solar composition from the envelope. We
suggest a multiple star scenario in which the SiC grains form in stellar
envelopes with slightly nonsolar initial Si isotope composition and
metallicities from one-half solar to solar. The initial Si abundances
are inferred from considerations of galactic chemical evolution,
coupling spectroscopic observations of abundances in stars of different
metal content with current predictions of stellar nucleosynthesis. The
isotopes Si-29 and Si-30 are assumed to be entirely produced by
short-lived massive stars exploding as supernovae, which also contribute
approximately 70% of the solar Si-28 abundance, the remaining
approximately 30% coming from long-lived stars, evolving in binary
systems, and leading to supernovae of Type Ia. More detailed
calculations of the Si isotopes yields from stars of various mass and
initial metallicity are, however, required, and a better understanding
of how the nucleosynthetic ejecta by supernovae are well homogenized
with the interstellar matter. Even the Ti isotope anomalies in SiC
grains cannot be explained as only an s-process signature. The linear
correlation shown by Ti and Si anomalies indicates that a similar
approach can be used to interpret the Ti anomalies as a mixture of a
pure s-component and of a variable nonsolar isotopic composition
initially present in the envelope of carbon stars. The question of the
large abundance of extinct Al-26 in many SiC grains is also considered.
We find that the production of Al-26 in the H shell of thermally pulsing
AGB stars, although followed by substantial consumption by neutron
captures during He thermal pulses, can account for the high Al-26/Al-27
ratios. The spread of carbon anomalies is interpreted as a consequence
of an initial spread of C-12/C-13 as observed in M stars and of the
subsequent enrichment in C-12 of the envelope during thermal pulses.
Finally, the nitrogen isotope anomalies are discussed
Intern experience at CH���M Hill, Inc.: an internship report
No full textIncludes author's vita"Submitted to the College of Engineering of Texas A&M University in partial
fulfillment of the requirement for the degree of Doctor of Engineering."Includes bibliographical referencesA review of the author's internship experience with CH���M HILL, Inc.
during the period September 1975 through May 1976 is presented. During this nine month
internship the author worked as an Engineer II in the Industrial Processes discipline of this
large consulting engineering firm... The author's prime responsibility was as one of three
lead design engineers on the design of a large wastewater treatment facility for a pulp mill
in Hoquiam, Washington owned by ITT Rayonier Inc. The work generally consisted of the design
of individual treatment units and associated piping and pumping. The purpose of the project
was to provide wastewater treatment capabilities that would satisfy the effluent limitations
(standards) imposed upon the mill by the State of Washington Department of Ecology and the
U.S. Environmental Protection Agency. The author's assignment also entailed necessary
interaction with the project manager and other CH���M HILL design engineers and support staff
members, the client's representatives, and representatives of two other consulting engineering
firms working on the project. Thus, the internship position at CH���M HILL provided considerable
experience coordinating the author's work with the work of other engineers, guiding the design
and administrative efforts of a support staff, and interacting regularly with the client and
other consulting firms. This broad exposure to a variety of engineering and organizational
problems provided a valuable educational experience
On the production of heavy neutron-rich isotopes during He and C burning in massive stars
No full textThe main purpose of this lecture is a re-examination of the yields of
s-elements by massive short-lived stars. He-burning conditions are
reviewed and results are presented for the nucleosynthesis in this
phase. The authors briefly analyse the possibility of n-captures during
carbon burning and discuss the contribution of massive stars to the
enrichment of the interstellar medium in s-elements
Simulation of thermal plant optimization and hydraulic aspects of thermal distribution loops for large campuses
No full textFollowing an introduction, the author describes Texas A&M University and its utilities system. After that, the author presents how to construct simulation models for chilled water and heating hot water distribution systems. The simulation model was used in a $2.3 million Ross Street chilled water pipe replacement project at Texas A&M University. A second project conducted at the University of Texas at San Antonio was used as an example to demonstrate how to identify and design an optimal distribution system by using a simulation model. The author found that the minor losses of these closed loop thermal distribution systems are significantly higher than potable water distribution systems. In the second part of the report, the author presents the latest development of software called the Plant Optimization Program, which can simulate cogeneration plant operation, estimate its operation cost and provide optimized operation suggestions. The author also developed detailed simulation models for a gas turbine and heat recovery steam generator and identified significant potential savings. Finally, the author also used a steam turbine as an example to present a multi-regression method on constructing simulation models by using basic statistics and optimization algorithms. This report presents a survey of the author??s working experience at the Energy Systems Laboratory (ESL) at Texas A&M University during the period of January 2002 through March 2004. The purpose of the above work was to allow the author to become familiar with the practice of engineering. The result is that the author knows how to complete a project from start to finish and understands how both technical and nontechnical aspects of a project need to be considered in order to ensure a quality deliverable and bring a project to successful completion. This report concludes that the objectives of the internship were successfully accomplished and that the requirements for the degree of Degree of Engineering have been satisfied
Isotopic Anomalies in Cr, Fe and Ni from ``s'' Processing in AGB Stars
No full textThe Fe group nuclei ^54Cr, ^58Fe, and ^64Ni are readily produced in AGB stars during "s" processing. These nuclides do not require SNe production. ..
VizieR Online Data Catalog: Infrared photometry of mass-losing AGB stars (Guandalini+, 2008)
No full textTables 11 and 12 present the data of the "Sub-sample D" discussed in the paper. In particular, Table 11 shows for each source the different denominations, the coordinates, spectral type, variability type and period. Instead, photometric fluxes in near- and mid-infrared, apparent bolometric magnitudes and an indication if the star is Intrinsic or Extrinsic are reported in Table 12. (2 data files). ..
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