Stress waves in transversely isotropic media: The homogeneous problem

The homogeneous problem of stress wave propagation in unbounded transversely isotropic media is analyzed. By adopting plane wave solutions, the conditions for the existence of the solution are established in terms of phase velocities and directions of particle displacements. Dispersion relations and group velocities are derived from the phase velocity expressions. The deviation angles (e.g., angles between the normals to the adopted plane waves and the actual directions of their propagation) are numerically determined for a specific fiber-glass epoxy composite. A graphical method is introduced for the construction of the wave surfaces using magnitudes of phase velocities and deviation angles. The results for the case of isotropic media are shown to be contained in the solutions for the transversely isotropic media

Wave propagation in anisotropic medium due to an oscillatory point source with application to unidirectional composites

The far-field displacements in an infinite transversely isotropic elastic medium subjected to an oscillatory concentrated force are derived. The concepts of velocity surface, slowness surface and wave surface are used to describe the geometry of the wave propagation process. It is shown that the decay of the wave amplitudes depends not only on the distance from the source (as in isotropic media) but also depends on the direction of the point of interest from the source. As an example, the displacement field is computed for a laboratory fabricated unidirectional fiberglass epoxy composite. The solution for the displacements is expressed as an amplitude distribution and is presented in polar diagrams. This analysis has potential usefulness in the acoustic emission (AE) and ultrasonic nondestructive evaluation of composite materials. For example, the transient localized disturbances which are generally associated with AE sources can be modeled via this analysis. In which case, knowledge of the displacement field which arrives at a receiving transducer allows inferences regarding the strength and orientation of the source, and consequently perhaps the degree of damage within the composite

Parameterized materials and dynamic response characterizations in unidirectional composites

The values of phase velocities of ultrasonic waves in transversely isotropic media are presented in terms of the fiber volume fraction of a unidirectional fiberglass epoxy composite with constant matrix properties and the ratio between extensional moduli in the longitudinal and transverse directions of the composite when the properties of the fibers are changed, at a constant fiber volume fraction. The model of a homogeneous transversely isotropic medium is adopted to describe the relations between elastic properties and velocities. The displacements due to an oscillatory point source in an infinite medium are used as one measure of comparison of the behavior of the unidirectional composite according to the variations of the parameters, as described above. Values of phase velocities, elastic moduli, Poisson's ratios and displacements due to a point source can be read from the parameterized plots for a known fiber volume fraction or a known ratio between extensional moduli of the composite. Alternatively fiber volume fraction and the ratio between extensional moduli can be inferred from the plots when the values of the phase velocities are known; for example from experimental measurements. Therefore, such parameterized curves may be useful in nondestructive mechanical property and material degradation characterizations

Towards a Semantic Gas Source Localization under Uncertainty

Towards a Semantic Gas Source Localization under Uncertainty.Communications in Computer and Information Science book series (CCIS, volume 855), doi:10.1007/978-3-319-91479-4_42This work addresses the problem of efficiently and coherently locating a gas source in a domestic environment with a mobile robot, meaning efficiently the coverage of the shortest distance as possible and coherently the consideration of different gas sources explaining the gas presence. The main contribution is the exploitation, for the first time, of semantic relationships between the gases detected and the objects present in the environment to face this challenging issue. Our proposal also takes into account both the uncertainty inherent in the gas classification and object recognition processes. These uncertainties are combined through a probabilistic Bayesian framework to provide a priority-ordered list of (previously observed) objects to check. Moreover the proximity of the different candidates to the current robot location is also considered by a cost function, which output is used for planning the robot inspection path. We have conducted an initial demonstration of the suitability of our gas source localization approach by simulating this task within domestic environments for a variable number of objects, and comparing it with an greedy approach.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Magnetically controlled exciton transfer in hybrid quantum dot-quantum well nanostructures

A magnetophotoluminescence study of the carrier transfer with hybrid InAs/GaAs quantum dot(QD)-InGaAs quantum well (QW) structures is carried out where we observe an unsual dependence of the photoluminescence (PL) on the GaAs barrier thickness at strong magnetic field and excitation density. For the case of a thin barrier the QW PL intensity is observed to increase at the expense of a decrease in the QD PL intensity. This is attributed to changes in the interplane carrier dynamics in the QW and the wetting layer (WL) resulting from increasing the magnetic field along with changes in the coupling between QD excited states and exciton states in the QW and the WL

Characterization, Classification And Analysis Of The Main Properties Of The Southwestern Goias Soil

Characterization of the soil and the grouping of its properties through main component analysis can assist in the classification and observation of the consequences of the conversion of native forest areas in pastures. Such data can aid in management practices. Considering the lack of studies in Cerrado soils of south-western Goias, developed metagranites of Jurubatuba suite, the objective was to classify and study the physical, chemical and mineralogical soil (under native forest and pasture) Southwest of Goias. Soil sampling and classification followed the Field Methods Manual and the Brazilian System of Soil Classification, respectively. The physical, chemical and mineralogical soil were studied, as well as main component analysis made for these attributes. The profile 1 under native forest was classified as "Cambissolo Háplico Tb eutrófico latossólico". The profile 2 under degraded pasture was rated "Latossolo Amarelo eutrófico típico". In addition, the profile 3 under rotated pasture was rated as "Latossolo Vermelho eutrófico chernossólico". It was observed that the "Latossolos" have higher bulk density and soil penetration resistance, indicating greater soil compaction. They showed high amounts of iron oxides and minor amount of nutrients such as calcium and magnesium. The principal component analysis allowed the grouping of profiles into two groups. Group 1 brought together the properties related to "Latossolos", and the second was related to "Cambissolo" properties. Thus, the principal components analysis aids the understanding of soil properties and the grouping of soils with similar characteristics, the level of order and management.3731135115

Modes of vibration on sqaure fiberglass epoxy composite thick plate

The frequencies and nodal patterns of a square thick plate of unidirectional fiberglass epoxy composite are measured experimentally. The constituent material is transversely isotropic. The plate is transversely excited at the center of the upper face, its resonant frequencies in the frequency range of 3 kHz to 21.73 kHz are detected and the measured nodal patterns are sketched

Evaluation of vineyard growth under four irrigation regimes using vegetation and soil on-the-go sensors

Precision agriculture is a useful tool to assess plant growth and development in vineyards. The present study focused on spatial and temporal analysis of vegetation growth variability, in four irrigation treatments with four replicates. The research was carried out in a vineyard located in the southwest of Spain during the 2012 and 2013 growing seasons. Two multispectral sensors mounted on an all-terrain vehicle (ATV) were used in the different growing seasons/stages in order to calculate the vineyard normalized difference vegetation index (NDVI). Soil apparent electrical conductivity (ECa) was also measured up to 0.8m soil depth using an on-the-go geophysical sensor. All measured data were analysed by means of principal component analysis (PCA). The spatial and temporal NDVI and ECa variations showed relevant differences between irrigation treatments and climatological conditions

Somatic cell nuclear transfer is associated with altered expression of angiogenic factor systems in bovine placentomes at term

Low efficiency of somatic cell cloning by nuclear transfer has been associated with alterations of placental vascular architecture. Placental growth and function depend on the growth of blood vessels; VEGF-A and bFGF are the most important factors controlling neovascularization and vascular permeability in the placenta. We hypothesize that the VEGF-A and bFGF systems are disrupted in placentomes from cloned animals, contributing to the placental abnormalities that are common in these clones. We determined mRNA expression and protein tissue localization of VEGF-A, bFGF, and their receptors in placentomes from cloned and non-cloned bovine fetuses at term. Real-time RT-PCR revealed that VEGFR-2 mRNA was increased in cloned male-derived placentomes, while mRNA of bFGF and its receptors were decreased in placentomes of cloned females. VEGF-A system proteins were found to be located in placentomal endothelial, maternal and fetal epithelial and stromal cells; there was a variable pattern of cellular distribution of these proteins in both cloned and non-cloned animals. Alterations in the expression of VEGF-A and bFGF systems suggest that angiogenic factors are involved in abnormal placental development in cloned gestations, contributing to impaired fetal development and poor survival ratesFAPESP 02/07392-7CAPES (PROBRAL grant 272/7)\ud CAPES (PROBRAL grant D/06/33937

Energy efficiency in agriculture. Showcase and alternatives for wheat production in Portugal.

This chapter presents some results obtained in the KBBE.2011.4-04 project “Energy Efficiency in Agriculture - AGREE” supported by the 7th Framework Program. It gives an overview into energy use and energy efficiency in wheat production in various agro-climatic zones of Europe. Among cereals, wheat is the crop with the largest cultivated area in Europe. In 2008, the percentage share of the area occupied by common and durum wheat in the countries analysed in the AGREE project ranged from 2.4% in Portugal to 18.9% in Germany (Gołaszewski et al., 2012). The different production systems in different climates vary substantially in their energy use and energy saving potential. A showcase of conventional wheat production in Portugal, where in 2012 it was cultivated in 54,761 ha (INE, 2013), is presented and some production alternatives are analysed. The main objective was to analyse the effect in the economic results, energy consumption and environmental impacts of three wheat production systems alternatives: 1. no tillage cropping systems, 2. reduction of phosphorous application and 3. the use of supplemental irrigation