8,951 research outputs found
Inspection and diagnosis tests for structural safety evaluation: A case study
Diagnosis and assessment of existing structures is a developing area due to the appearance of a high number of building defects, structural and non-structural deterioration and precocious loss of quality, and, consequently, lower expected durability. With the aim of verifying the viability of rehabilitation or the need to demolish an existing fifteen year old parking building, several inspections and diagnostic non-destructive and destructive testing, visual inspection, were carried out to evaluate the structural safety conditions
Error-correcting code on a cactus: a solvable model
An exact solution to a family of parity check error-correcting codes is
provided by mapping the problem onto a Husimi cactus. The solution obtained in
the thermodynamic limit recovers the replica symmetric theory results and
provides a very good approximation to finite systems of moderate size. The
probability propagation decoding algorithm emerges naturally from the analysis.
A phase transition between decoding success and failure phases is found to
coincide with an information-theoretic upper bound. The method is employed to
compare Gallager and MN codes.Comment: 7 pages, 3 figures, with minor correction
Typical performance of low-density parity-check codes over general symmetric channels
Typical performance of low-density parity-check (LDPC) codes over a general
binary-input output-symmetric memoryless channel is investigated using methods
of statistical mechanics. Theoretical framework for dealing with general
symmetric channels is provided, based on which Gallager and MacKay-Neal codes
are studied as examples of LDPC codes. It has been shown that the basic
properties of these codes known for particular channels, including the property
to potentially saturate Shannon's limit, hold for general symmetric channels.
The binary-input additive-white-Gaussian-noise channel and the binary-input
Laplace channel are considered as specific channel noise models.Comment: 10 pages, 4 figures, RevTeX4; an error in reference correcte
Identification of mineral components in tropical soils using reflectance spectroscopy and advanced spaceborne thermal emission and reflection radiometer (ASTER) data.
Soil characteristics provide important support for understanding transformations that occur in environmental systems. Physical characteristics and chemical compositions of soils controlled by pedogenetic processes, climatic changes and land use imply different types of environmental transformations. Reflectance spectroscopy is an alternative soil mapping technique that uses spectral absorption features between visible (VIS) and short-wave infrared (SWIR) wavelengths (0.3?2.5 μm) for determining soil mineralogy. Soil analysis by means of reflectance spectroscopy and orbital optical sensors have provided favorable results in mapping transformation processes in environmental systems, particularly in arid and semiarid climates in extra-tropical terrains. In the case of inter-tropical environments, these methods cannot be readily applied due to local factors such as lack of exposed regolith, high amounts of soil moisture and the presence of dense vegetation. This study uses Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and reflectance spectroscopy data to map mineral components of soils covering a part of the state of São Paulo, Brazil, which could be linked to key aspects of environmental transformations in this tropical area (e.g., climate change, shifts in agriculture fronts, ph, and soil characteristics). We collected forty-two (42) soil samples at a depth of 0?20 cm, considering that this superficial layer corresponds to the highest correlation with soil properties detected by the ASTER sensor. These samples were measured using a FieldSpec FR spectrometer, and the derived spectra were interpreted for mineral composition. Interpretation was supported by X-ray diffraction analysis on the same samples. The spectral signatures were re-sampled to ASTER VNIR (AST1-4: 0.52?0.86 μm) and SWIR (AST5-9: 1.60?2.43 μm) spectral bandwidths and validated by comparing reflectance spectra of field samples with those extracted from atmospherically corrected and calibrated ASTER pixels. The agreement between spectral signatures measured from soil samples and those derived from ASTER imagery pixels proved plausible, with R2 correlation values ranging from 0.6493 to 0.7886. This signifies that diagnostic spectral features of key minerals in tropical soils can be mapped at the spectral resolution of 9-band ASTER VNIR through SWIR reflectance. We used these spectral signatures as end-members in hyperspectral routine classifications adapted for use with ASTER data. Results proved possible the identification and remote mapping of minerals such as kaolinite, montmorillonite and gibbsite, as well as the distinction between iron-rich and iron-poor soils
Caracterização construtiva e de anomalias correntes nos edifícios de alvenaria de adobe: o caso de estudo de Aveiro
As inspecções realizadas a edifícios em alvenaria de adobe na cidade de
Aveiro permitiram efectuar um levantamento construtivo e patológico desse
património singular. Partindo dos relatórios elaborados, o presente artigo faz
uma síntese das características construtivas dos edifícios inspeccionados,
relativamente aos tipos de paredes, à constituição das estruturas em madeira
quer dos pavimentos quer das coberturas, e ainda expõe e comenta as anomalias
mais correntes
On the heating of source of the Orion KL hot core
We present images of the J=10-9 rotational lines of HC3N in the vibrationally
excited levels 1v7, 1v6 and 1v5 of the hot core (HC) in Orion KL. The images
show that the spatial distribution and the size emission from the 1v7 and 1v5
levels are different. While the J=10-9 1v7 line has a size of 4''x 6'' and
peaks 1.1'' NE of the 3 mm continuum peak, the J=10--9 1v5 line emission is
unresolved (<3'') and peaks 1.3'' south of the 3 mm peak. This is a clear
indication that the HC is composed of condensations with very different
temperatures (170 K for the 1v7 peak and K for the 1v5 peak). The
temperature derived from the 1v7 and 1v5 lines increases with the projected
distance to the suspected main heating source I. Projection effects along the
line of sight could explain the temperature gradient as produced by source I.
However, the large luminosity required for source I, >5 10^5 Lsolar, to explain
the 1v5 line suggests that external heating by this source may not dominate the
heating of the HC. Simple model calculations of the vibrationally excited
emission indicate that the HC can be internally heated by a source with a
luminosity of 10^5 Lsolar, located 1.2'' SW of the 1v5 line peak (1.8'' south
of source I). We also report the first detection of high-velocity gas from
vibrationally excited HC3N emission. Based on excitation arguments we conclude
that the main heating source is also driving the molecular outflow. We
speculate that all the data presented in this letter and the IR images are
consistent with a young massive protostar embedded in an edge-on disk.Comment: 13 pages, 3 figures, To be published in Ap.J. Letter
Parathyroid Cyst: Differential Diagnosis
Parathyroid cysts are rare lesions of the cervical region and less frequently of the mediastinum. They occur mostly in women and are usually asymptomatic. They generally occur in the fourth and fifth decades of life and mainly are non-functioning. They commonly present as a neck mass that is found incidentally during surgery or in imaging test. Its importance lies in the difficulty in diagnosis, often confusing itself with thyroid pathology. The diagnosis is usually made intraoperatively, confirmed by histopathological examination.The aim of this paper is to report a case of parathyroid cyst that mimics a thyroid nodule.info:eu-repo/semantics/publishedVersio
Tailored graph ensembles as proxies or null models for real networks I: tools for quantifying structure
We study the tailoring of structured random graph ensembles to real networks,
with the objective of generating precise and practical mathematical tools for
quantifying and comparing network topologies macroscopically, beyond the level
of degree statistics. Our family of ensembles can produce graphs with any
prescribed degree distribution and any degree-degree correlation function, its
control parameters can be calculated fully analytically, and as a result we can
calculate (asymptotically) formulae for entropies and complexities, and for
information-theoretic distances between networks, expressed directly and
explicitly in terms of their measured degree distribution and degree
correlations.Comment: 25 pages, 3 figure
The image of and the interest in the accounting profession: an empirical study in three social groups
This study has the following goals: to analyse the image of and the interest in the accounting profession; to identify any possible differences in perception among the respondent groups; to identify the individual characteristics influencing the perception; to propose an explanatory model of the interest in the profession. The respondents were the members of three social groups composing the profession’s value chain: 105 financial officers of the biggest 500 Portuguese companies; 412 chartered accountants; 235 students majoring in Accounting. The data collected show that there are not any significant differences in perception regarding the image of and the interest in the accounting profession. Regarding the influence of the individual characteristics, the results obtained lead to the following conclusion: the third-year students with a higher average perceive a higher level of interest in the profession; the professionals with a higher academic degree and college graduated perceive a lower level of interest in the profession.info:eu-repo/semantics/acceptedVersio
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