A Hybrid Approach for Modeling Stochastic Ray Propagation in Stratified Random Lattices

The present contribution deals with ray propagation in semi-innite percolation lattices consisting of a succession of uniform density layers. The problem of analytically evaluating the probability that a single ray penetrates up to a prescribed level before being reected back into the above empty half-plane is addressed. A hybrid approach, exploiting the complementarity of two mathematical models in dealing with uniform congurations, is presented and assessed through numerical ray-tracing-based experiments in order to show improvements upon previous predictions techniques. "The definitive version is available at www3.interscience.wiley.com

A Hybrid Approach Based on PSO and Hadamard Difference Sets for the Synthesis of Square Thinned Arrays

A hybrid approach for the synthesis of planar thinned antenna arrays is presented. The proposed solution exploits and combines the most attractive features of a particle swarm algorithm and those of a combinatorial method based on the noncyclic difference sets of Hadamard type. Numerical experiments validate the proposed solution, showing improvements with respect to previous results. (c) 2009 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works

Percolation-Based Approaches For Ray-Optical Propagation in Inhomogeneous Random Distribution of Discrete Scatterers

We address the problem of optical ray propagation in an inhomogeneous half�]plane lattice, where each cell can be occupied according to a known one�]dimensional obstacles density distribution. A monochromatic plane wave impinges on the random grid with a known angle and undergoes specular reflections on the occupied cells. We present two different approaches for evaluating the propagation depth inside the lattice. The former is based on the theory of the Martingale random processes, while in the latter ray propagation is modelled in terms of a Markov chain. A numerical validation assesses the proposed solutions, while validation through experimental data shows that the percolation model, in spite of its simplicity, can be applied to model real propagation problems

Computationally-Effective Optimal Excitation Matching for the Synthesis of Large Monopulse Arrays

Antenna arrays able to generate two different patterns are widely used in tracking radar systems [1]. Optimal (in the Dolph�]Chebyshev sense) sum [2] and difference patterns [3] can be generated by using two independent feed networks. Unfortunately, such a situation generally turns out to be impracticable because of its costs, the occupied physical space, the circuit complexity, and electromagnetic interferences. Thus, starting from the optimal sum pattern a sub�]optimal solution for the difference pattern is usually synthesized by means of the sub�]array technique. The array elements are grouped in sub�]arrays properly weighted for matching the constrains of the difference beam. Finding the best elements grouping and the sub�]array weights is a complex and challenging research topic, especially when dealing with large arrays. As far as linear arrays are concerned, McNamara proposed in [4] an analytical method for determining the �gbest compromise�h difference pattern. Unfortunately, when the ratio between the elements of the array and sub�]arrays increases, such a technique exhibits several limitations mainly due to the ill�]conditioning of the problem and the computational costs due to exhaustive evaluations. A non�]negligible saving might be achieved by applying optimization algorithms (see for instance [5] and [6]) aimed at minimizing a suitable cost function. Notwithstanding, optimization�]based approaches still appear computationally expensive when dealing with large arrays because of wide dimension of solution space to be sampled. In order to properly deal with these computational issues, this contribution presents an innovative approach based on an optimal excitation matching procedure. By exploiting the relationship between independently�]optimal sum and difference patterns, the dimension of the solution space is considerably reduced and efficiently sampled by taking into account the presence of array elements more suitable to change sub�]array membership. In the following, the proposed technique is described pointing out, through a representative case, its potentialities and effectiveness in dealing with large arrays. This is the author's version of the final version available at IEEE

Stochastic Ray Propagation in Stratified Random Lattices – Comparative Assessment of Two Mathematical Approaches

In this report, ray propagation in stratified semi-infinite percolation lattices consisting of a succession of uniform density layers is considered. The final version of this article is available at the url of the journal PIER: http://www.jpier.org/PIER

An innovative approach based on a tree-searching algorithm for the optimal matching of independently optimum sum and difference excitations

An innovative approach for the optimal matching of independently optimum sum and difference patterns through sub-arrayed monopulse linear arrays is presented. By exploiting the relationship between the independently optimal sum and difference excitations, the set of possible solutions is considerably reduced and the synthesis problem is recast as the search of the best solution in a non-complete binary tree. Towards this end, a fast resolution algorithm that exploits the presence of elements more suitable to charge sub-array membership is presented. The results of a set of numerical experiments are reported in order to validate the proposed approach pointing out its effectiveness also in comparison with state-of-the-art optimal matching techniques. (c) 2008 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works

Isolated olecranon fractures in children affected by osteogenesis imperfecta type I treated with single screw or tension band wiring system: outcomes and pitfalls in relation to bone mineral density

The purpose of this study is to compare the results of 2 techniques, tension band wiring (TBW) and fixation with screws, in olecranon fractures in children affected with osteogenesis imperfecta (OI) type I. Between 2010 and 2014, 21 olecranon fractures in 18 children with OI (average age: 12 years old) were treated surgically. Ten patients were treated with the screw fixation and 11 with TBW. A total of 65% of olecranon fractures occurred as a result of a spontaneous avulsion of the olecranon during the contraction of the triceps muscle. The average follow-up was 36 months. Among the children treated with 1 screw, 5 patients needed a surgical revision with TBW due to a mobilization of the screw. In this group, the satisfactory results were 50%. In patients treated with TBW, the satisfactory results were 100% of the cases. The average Z-score, the last one recorded in the patients before the trauma, was -2.53 in patients treated with screw fixation and -2.04 in those treated with TBW. TBW represents the safest surgical treatment for patients suffering from OI type I, as it helps to prevent the rigidity of the elbow through an earlier recovery of the range of motion, and there was no loosening of the implant. In analyzing the average Z-score before any fracture, the fixation with screws has an increased risk of failure in combination with low bone mineral density

Cosa guardiamo quando guardiamo? I limiti del visualismo nel definire l’autenticità dell’esperienza nell’antropologia del turismo

In this paper I investigate the way by which the anthropology of the senses and perceptions affects tourist’s experience. By utilizing the concept of authenticity and the way it is outlined by its existential value (Wang 1999), or as process of authentication (Van de Port 2004; Cohen & Cohen 2012), my aim is to show how it is negotiated and mediated with, amongst other, through the senses. In the specific field of tourism, although anthropology nowadays strives to regain more room to analyse the other senses, the one most linked to the tourist’s experience is sight. It is considered in this context as a set of gazes that the tourist imposes or is subjected to in his relationship with the Other, employing the camera as a medium that, as Sontag and Barthes affirm, is a weapon by which the gaze is limited, oriented and negotiated.In this paper I investigate the way by which the anthropology of the senses and perceptions affects tourist’s experience. By utilizing the concept of authenticity and the way it is outlined by its existential value (Wang 1999), or as process of authentication (Van de Port 2004; Cohen & Cohen 2012), my aim is to show how it is negotiated and mediated with, amongst other, through the senses. In the specific field of tourism, although anthropology nowadays strives to regain more room to analyse the other senses, the one most linked to the tourist’s experience is sight. It is considered in this context as a set of gazes that the tourist imposes or is subjected to in his relationship with the Other, employing the camera as a medium that, as Sontag and Barthes affirm, is a weapon by which the gaze is limited, oriented and negotiated

Sind alle Menschen gleich(wertig)? Die Antworten der Religionen auf die Frage nach der Begründung unterschiedlicher sozialer Stände und Wertungen

Die verschiedenen Religionen geben unterschiedliche Antworten auf die Frage nach den sozialen Ständen. Es gibt Religionen (wie z. B. den Hinduismus), die eine konstituierende Rolle für das entsprechende Gesellschaftssystem spielen, und es gibt solche (wie z. B. das Christentum oder den Buddhismus), die eine Gesellschaftsordnung vorfinden und diese bewerten bzw. sich dazu in entsprechender Weise verhalten. Gemeinsam ist allen Religionen, dass sie das Bild einer idealen Ordnung des Zusammenlebens vermitteln, die mit ihrer grundsätzlichen Sinngebung und ihren jeweiligen Heilszielen korrelieren.The religions hold very different positions regarding the questions of social status and their role in society. Some religions are constitutive for the social system, while others developed first in elder systems and then implanted their critical reflections and moral views into these systems. Common to all religions is an ethical point of view and a sense-giving function. But the ideals for living together are very different

Osteoclast differentiation from human blood precursors on biomimetic calcium-phosphate substrates

The design of synthetic bone grafts to foster bone formation is a challenge in regenerative medicine. Understanding the interaction of bone substitutes with osteoclasts is essential, since osteoclasts not only drive a timely resorption of the biomaterial, but also trigger osteoblast activity. In this study, the adhesion and differentiation of human blood-derived osteoclast precursors (OCP) on two different micro-nanostructured biomimetic hydroxyapatite materials consisting in coarse (HA-C) and fine HA (HA-F) crystals, in comparison with sintered stoichiometric HA (sin-HA, reference material), were investigated. Osteoclasts were induced to differentiate by RANKL-containing supernatant using cell/substrate direct and indirect contact systems, and calcium (Ca++) and phosphorus (P5+) in culture medium were measured. We observed that OCP adhered to the experimental surfaces, and that osteoclast-like cells formed at a rate influenced by the micro- and nano-structure of HA, which also modulate extracellular Ca++. Qualitative differences were found between OCP on biomimetic HA-C and HA-F and their counterparts on plastic and sin-HA. On HA-C and HA-F cells shared typical features of mature osteoclasts, i.e. podosomes, multinuclearity, tartrate acid phosphatase (TRAP)-positive staining, and TRAP5b-enzyme release. However, cells were less in number compared to those on plastic or on sin-HA, and they did not express some specific osteoclast markers. In conclusion, blood-derived OCP are able to attach to biomimetic and sintered HA substrates, but their subsequent fusion and resorptive activity are hampered by surface micro-nano-structure. Indirect cultures suggest that fusion of OCP is sensitive to topography and to extracellular calcium.Preprin