Optical micro-structures fabricated on top of optical fibers by means of two-photon photopolymerization

In this work we report, for the first time to our knowledge, the possibility to fabricate various structures, with good optical proprieties, on the top of optical fibers, using the two-photon lithography (TPL) technique. We show the convenience of this approach to quickly create generic 3D shapes using a single set-up by contrast to past shape-dependent methods. A set of different structures are fabricated and characterized to demonstrate the versatility of this approach and their high optical quality.     

The territorial and landscape impacts of photovoltaic systems: Definition of impacts and assessment of the glare risk

The installation and operation of systems that exploit solar energy through photovoltaic conversion, recently promoted in some European countries by new sell-back tariffs, is a relevant transformation of the territory for various reasons (land use, elimination of the existing vegetation, visual impact on the components of the landscape, microclimate change, glare from the reflection of the direct sunlight). The weak energy intensity of the solar source coupled with the low conversion efficiency of the photovoltaic cells, make the physical dimensions of such systems relevant and, with them, also the environmental, territorial and landscape impacts that basically depend on the physical extent of the system. If it is well known that an incentive to the exploitation of renewable sources is one of the features of the policy of land conservation, including the one of the protected areas, at the same time the concerns of local communities and governments about the environmental, territorial and landscape impacts of this technology are increasing rapidly.Given this picture, this work is intended to clarify the territorial impacts of the ground mounted photovoltaic systems. Later, the paper concentrates on a specific impact, which is the assessment of the risk of glare by reflection of direct sunlight from the surfaces of photovoltaic modules. The methodologies that can be used to assess this impact and the outcomes of an evaluation carried out for a 5000 m² PV system currently designed on a hilly territory in Italy are presented.     

Small Area Drawings of Outerplanar Graphs

We show three linear-time algorithms for constructing planar straight-line grid drawings of outerplanar graphs. The first and the second algorithm are for balanced outerplanar graphs. Both require linear area. The drawings produced by the first algorithm are not outerplanar while those produced by the second algorithm are. On the other hand, the first algorithm constructs drawings with better angular resolution. The third algorithm constructs outerplanar drawings of general outerplanar graphs with O(n ^1.48) area. Further, we study the interplay between the area requirements of the drawings of an outerplanar graph and the area requirements of a special class of drawings of its dual tree. Work partially supported by MUR under Project MAINSTREAM Algorithms for Massive Information Structures and Data Streams.     

On the Tolerance to Manufacturing Defects in Molecular QCA Tiles for Processing-by-wire

Among emerging technologies, Quantum-dot Cellular Automata (QCA) relies on innovative computational paradigms. For nano-scale implementation, the so-called processing-by-wire (PBW) paradigm in QCA is very effective as processing takes place, while signal communication is accomplished. This paper analyzes the defect tolerance properties of PBW for manufacturing tiles by molecular QCA cells. Based on a 3?×?3 grid and various input/output arrangements in QCA cells, different tiles are analyzed and simulated using a coherence vector engine. The functional characterization and polarization level of these tiles for undeposited cell defects are reported and detailed profiles are provided. It is shown that novel features of PBW are possible due to the spatial redundancy of the cells in the tiles that permits to retain at high probability the fault free function in the presence of defects. Moreover, it is shown that QCA tiles are robust and inherently tolerant to cell defects (by logic equivalence, also additional cell defects can be accommodated).     

Lower bounds on the rotation distance of binary trees

The rotation distanced(S,T) between two binary trees S, T of n vertices is the minimum number of rotations to transform S into T. While it is known that d(S,T)?2n−6, a well-known conjecture states that there are trees for which this bound is sharp for any value of n?11. We are unable to prove the conjecture, but we give here some simple criteria for lower bound evaluation, leading for example to individuate some “regular” tree structures for which d(S,T)=3n/2−O(1), or d(S,T)=5n/3−O(1).     

A Novel Approach to Fiber-Optic Tweezers: Numerical Analysis of the Trapping Efficiency

We present a novel all-fiber optical tweezer (OT) for biological applications. The tweezer is based on a new approach relying on total internal reflection in an annular core fiber or into a fiber bundle. The proposed device, whose trapping efficacy has been recently demonstrated experimentally, is extremely promising, also because optical manipulation and analysis functions can be easily added to the tweezer basic structure, leading to the realization of a powerful biotool. In this paper, a detailed numerical analysis of the structure properties and of its efficiency is carried out in the Mie regime. Moreover, by defining a new parameter to evaluate the trapping efficiency, we perform a comparison between the proposed tweezer structure and a standard OT based on a strongly focused Gaussian beam.     

Effects of scattering resonances on carrier-carrier entanglement in charged quantum dots

We address the problem of the entanglement generation in an electron-scattering by a 1D double-barrier resonant tunnelling device. In particular we analyze the role played by transport resonances in the appearance of quantum correlations between the energy states of the electrons. The entanglement is not sensitive to the presence of Breit-Wigner resonances, while it may be controlled by manipulating Fano resonances. Such a behavior is ascribed to the different mechanisms characterizing the two types of processes.     

Solving unit commitment problems with general ramp constraints

Lagrangian relaxation (LR) algorithms are among the most successful approaches for solving large-scale hydro-thermal unit commitment (UC) problems; this is largely due to the fact that the single-unit commitment (1UC) problems resulting from the decomposition, incorporating many kinds of technical constraints such as minimum up- and down-time requirements and time-dependent startup costs, can be efficiently solved by dynamic programming (DP) techniques. Ramp constraints have historically eluded efficient exact DP approaches; however, this has recently changed [Frangioni A, Gentile C. Solving nonlinear single-unit commitment problems with ramping constraints. Oper Res 2006;54(4):767–75]. We show that the newly proposed DP algorithm for ramp-constrained (1UC) problems allows to extend existing LR approaches to ramp-constrained (UC); this is not obvious since the heuristic procedures typically used to recover a primal feasible solution are not easily extended to take ramp limits into account. However, dealing with ramp constraints in the subproblems turns out to be sufficient to provide the LR heuristic enough guidance to produce good feasible solutions even with no other modification of the approach; this is due to the fact that (sophisticated) LR algorithms to (UC) duly exploit the primal information computed by the Lagrangian Dual, which in the proposed approach is ramp feasible. We also show by computational experiments that the LR [approach] is competitive with those based on general-purpose mixed-integer program (MIP) solvers for large-scale instances, especially hydro-thermal ones.