Constitutive Model for Material Comminuting at High Shear Rate

The modeling of high velocity impact into brittle or quasibrittle solids is hampered by the unavailability of a constitutive model capturing the effects of material comminution into very fine particles. The present objective is to develop such a model, usable in finite element programs. The comminution at very high strain rates can dissipate a large portion of the kinetic energy of an impacting missile. The spatial derivative of the energy dissipated by comminution gives a force resisting the penetration, which is superposed on the nodal forces obtained from the static constitutive model in a finite element program. The present theory is inspired partly by Grady's model for comminution due to explosion inside a hollow sphere, and partly by analogy with turbulence. In high velocity turbulent flow, the energy dissipation rate is enhanced by the formation of micro-vortices (eddies) which dissipate energy by viscous shear stress. Similarly, here it is assumed that the energy dissipation at fast deformation of a confined solid gets enhanced by the release of kinetic energy of the motion associated with a high-rate shear strain of forming particles. For simplicity, the shape of these particles in the plane of maximum shear rate is considered to be regular hexagons. The rate of release of free energy density consisting of the sum of this energy and the fracture energy of the interface between the forming particle is minimized. The particle sizes are assumed to be distributed according to Schuhmann's power law. It is concluded that the minimum particle size is inversely proportional to the (2/3)-power of the shear strain rate, that the kinetic energy release is to proportional to the (2/3)-power, and that the dynamic comminution creates an apparent material viscosity inversely proportional to the (1/3)-power of the shear strain rate.Comment: 13 pages, 2 figure

Fano collective resonance as complex mode in a two dimensional planar metasurface of plasmonic nanoparticles

Fano resonances are features in transmissivity/reflectivity/absorption that owe their origin to the interaction between a bright resonance and a dark (i.e., sub-radiant) narrower resonance, and may emerge in the optical properties of planar two-dimensional (2D) periodic arrays (metasurfaces) of plasmonic nanoparticles. In this Letter, we provide a thorough assessment of their nature for the general case of normal and oblique plane wave incidence, highlighting when a Fano resonance is affected by the mutual coupling in an array and its capability to support free modal solutions. We analyze the representative case of a metasurface of plasmonic nanoshells at ultraviolet frequencies and compute its absorption under TE- and TM-polarized, oblique plane-wave incidence. In particular, we find that plasmonic metasurfaces display two distinct types of resonances observable as absorption peaks: one is related to the Mie, dipolar resonance of each nanoparticle; the other is due to the forced excitation of free modes with small attenuation constant, usually found at oblique incidence. The latter is thus an array-induced collective Fano resonance. This realization opens up to manifold flexible designs at optical frequencies mixing individual and collective resonances. We explain the physical origin of such Fano resonances using the modal analysis, which allows to calculate the free modes with complex wavenumber supported by the metasurface. We define equivalent array dipolar polarizabilities that are directly related to the absorption physics at oblique incidence and show a direct dependence between array modal phase and attenuation constant and Fano resonances. We thus provide a more complete picture of Fano resonances that may lead to the design of filters, energy-harvesting devices, photodetectors, and sensors at ultraviolet frequencies.Comment: 6 pages, 5 figure

Risk and career choice: Evidence from Turkey

In this paper, we examine the college major choice decision in a risk and return framework using university entrance exam data from Turkey. Specifically we focus on the choice between majors with low income risk such as education and health and others with riskier income streams. We use a unique dataset that allows us to control for the choice set of students and parental attitudes towards risk. Our results show that father's income, self-employment status and social security status are important factors influencing an individual in choosing a riskier career such as business over a less risky one such as education or health. © 2010 Elsevier Ltd

Etlik piliç kümeslerin su hatlarında Campylobacter coli varlığı

This study aimed to determine the presence of Campylobacter coli in water lines of commercial broiler houses. The samples were taken in the period of three sequential focks in two houses. There was a distance of approximately 25 km between the houses and drinking water was supplied by groundwater in one house while the municipal water system with polyvinyl chloride plastic pipe was the source of drinking water in the other. C. coli was isolated and identified in drinking water and nipple swab samples, and fresh fecal dropping samples in both houses. The results of this study suggest that C. coli could be found in water-line of commercial broiler houses and drinking water might be a source for fock's colonization by C. coli

Groundwater level assessment and prediction in the Nebraska Sand Hills using LIDAR-derived lake water level

The spatial variability of groundwater levels is often inferred from sparsely located hydraulic head observations in wells. The spatial correlation structure derived from sparse observations is associated with uncertainties that spread to estimates at unsampled locations. In areas where surface water represents the nearby groundwater level, remote sensing techniques can estimate and increase the number of hydraulic head measurements. This research uses light detection and ranging (LIDAR) to estimate lake surface water level to characterize the groundwater level in the Nebraska Sand Hills (NSH), an area with few observation wells. The LIDAR derived lake groundwater level accuracy was within 40 cm mean square error (MSE) of the nearest observation wells. The lake groundwater level estimates were used to predict the groundwater level at unsampled locations using universal kriging (UK) and kriging with an external drift (KED). The results indicate unbiased estimates of groundwater level in the NSH. UK showed the influence of regional trends in groundwater level while KED revealed the local variation present in the groundwater level. A 10-fold cross-validation demonstrated KED with better mean squared error (ME) [–0.003, 0.007], root mean square error (RMSE) [2.39, 4.46], residual prediction deviation (RPD) [1.32, 0.71] and mean squared deviation ratio (MSDR) [1.01, 1.49] than UK. The research highlights that the lake groundwater level provides an accurate and cost-effective approach to measure and monitor the subtle changes in groundwater level in the NSH. This methodology can be applied to other locations where surface water bodies represent the water level of the unconfined aquifer and the results can aid in groundwater management and modeling

Rough Cilicia Archaeological Survey Project: Report of the 2002 Season

The Rough Cilicia Archaeological Project conducted archaeological and geoarchaeological research in the Gazipaşa area from July 20 through 1 September 2001. Several goals were met this season. Under the direction of Michael Hoff and Rhys Townsend, detailed plans were completed of monumental structures at the sites of Asar Tepe, Lamos, and Selinus. At Lamos, in particular, the team made a number of finds, including the discovery of an inscribed statue base of large size in a small podium complex on a hill above the so-called stadium

The Basilicata Wealth Fund: Resource Policy and Long-Run Economic Development in Southern Italy

This paper contributes to the growing political economy literature of within-country natural resources management, by proposing a new resource policy for the oil-rich southern Italian region of Basilicata. The policy proposal is to establish a (regional) wealth fund in which all the royalty revenues from non-renewable natural resource exploitation in Basilicata would be stored and fully converted into low-risk financial assets. The scope is to give priority to long-run investments as to better exploit revenues from large-scale extraction of natural capital. Establishing a wealth fund at the regional sub-national level is a novel approach that can be applied to other resource-rich regions in the world. I label the fund as the Basilicata Wealth Fund (BWF). The BWF would be a regionally owned investment fund, however independently administered from national authorities (for instance, as an independent legal entity under the jurisdiction of the Bank of Italy). In addition, the paper posits a transparent and clear-cut spending fiscal rule in order to let regional authorities use the resource revenues to finance economic policy. The clear advantage from the BWF would be the stronger focus on long-run economic development and the higher accountability, hence avoiding misuse of resource revenues for myopic fiscal spending

Optical character recognition on heterogeneous SoC for HD automatic number plate recognition system

Automatic number plate recognition (ANPR) systems are becoming vital for safety and security purposes. Typical ANPR systems are based on three stages: number plate localization (NPL), character segmentation (CS), and optical character recognition (OCR). Recently, high definition (HD) cameras have been used to improve their recognition rates. In this paper, four algorithms are proposed for the OCR stage of a real-time HD ANPR system. The proposed algorithms are based on feature extraction (vector crossing, zoning, combined zoning, and vector crossing) and template matching techniques. All proposed algorithms have been implemented using MATLAB as a proof of concept and the best one has been selected for hardware implementation using a heterogeneous system on chip (SoC) platform. The selected platform is the Xilinx Zynq-7000 All Programmable SoC, which consists of an ARM processor and programmable logic. Obtained hardware implementation results have shown that the proposed system can recognize one character in 0.63 ms, with an accuracy of 99.5% while utilizing around 6% of the programmable logic resources. In addition, the use of the heterogenous SoC consumes 36 W which is equivalent to saving around 80% of the energy consumed by the PC used in this work, whereas it is smaller in size by 95%

Dynamique du piégeage des micropolluants métalliques au sein des zones humides artificielles traitant des eaux pluviales urbaines strictes : Etude de cas à Strasbourg, Moulins-lès-Metz et Leuville-sur-Orge

Colloque avec actes et comité de lecture. internationale.International audienceStormwater constructed wetlands (SCW) in Strasbourg (Alsace, France), Moulin-lès-Metz (Lorraine, France), and Leuville-sur-Orge (Ile-de-France, France) receive and treat exclusively runoffs from urban catchments but with different soil uses. Made up of sedimentation ponds and a vertical subsurface flow constructed wetland, the treatment facilities lead to trap several trace metal pollution. Each site belongs to different hydroclimatic areas (modified oceanic, modified continental and semi-continental) and was designed for different purposes (watercourse protection in Strasbourg and in Leuville-sur-Orge, protection of drinking water wells in Moulins-lès-Metz). The aim of this study is to explore trace metals (Cd, Cu, Pb and Zn) behaviours in these SCW. We investigated trace metal trapping by determining concentrations in the systems compartments (filters media and plants). Then trace metal speciation was determined through sequencial extractions of the sediment and filter media. This allowed to determine their forms in soils and to anticipate their behaviour during physical and chemical condition changes. This study permits to obtain first results for the metals stability, to highlight a decrease of the concentrations through the SCW depth (from surficial sediment to clean filter media) and to observe a negligible metal trap in plants (mainly in roots)