1,720,979 research outputs found
Coherent perfect absorption in photonic structures
Get PDFThe ability to drive a system with an external input is a fundamental aspect of light-matter interaction. The coherent perfect absorption (CPA) phenomenon extends to the general multibeam interference phenomenology the well-known critical coupling concepts (Haus in Waves and fields in optoelectronics. Prentice-Hall, Englewood Cliffs, 1984; Yariv and Yeh in Optical Electronics in Modern Communication. Oxford University Press, New York, 2007). The latter detail the conditions under which the energy of the input field is fed in full to the absorbing element. In a multi-port system, the relative phase of the incoming fields can yield the ultimate control of the absorption, from CPA to complete transparency (coherent perfect transparency, CPT), and also beyond, in amplifying regimes, to laser threshold control (Longhi in Phys Rev A 82:031801, 2010; Sun et al. in Phys Rev Lett 112:143903, 2014). This interferometric control of absorption can be employed to reach perfect energy feeding into nanoscale systems such as plasmonic nanoparticles (Noh et al. in Phys Rev Lett 108(18):186805, 2012), and multi-port interference can be used to enhance the absorption when they are embedded in a strongly scattering system (Chong and Stone in Phys Rev Lett 107(16):163901, 2011), with potential applications to nanoscale sensing. Here we review the two-port CPA in reference to photonic structures which can resonantly couple to the external fields. A revised two-port theory of CPA is illustrated, which relies on the Scattering Matrix formalism and is valid for all linear two-port systems with reciprocity. Through a semiclassical approach, treating two-port critical coupling conditions in a non-perturbative regime, it is demonstrated that the strong-coupling regime and the critical coupling condition can indeed coexist; in this situation, termed strong critical coupling (Zanotto et al. in Nature Phys 10(11):830-834, 2014), all the incoming energy is converted into polaritons. Experimental results are presented, which clearly display the elliptical trace of absorption as function of input unbalance in a thin metallo-dielectric metamaterial, and verify polaritonic CPA in an intersubband polariton photonic crystal membrane resonator. Concluding remarks discuss the future perspectives of CPA with photonic structures
Natural Gas Consumption Forecasting for Anomaly Detection
No full textNatural gas consumption forecasting is critical for many gas supplier companies tasks - e.g. gas procurement optimization, pipe network monitoring, management and security. This paper presents the joint work we carried out with HERA S.p.A., Italian gas provider leader, which goal is to forecast gas consumption for a given gas network as well as detecting anomalous gas flows according to historic data so to facilitate the monitoring and security processes in their central control room.
Historic network conditions are sampled every 15 min, each sample is composed by a gas flow, an outside temperature, and the timestamp the sample was recorded. Descriptive analyses were carried out using historic data in a village and a small city, then two forecasting techniques were defined, one based on a nearest neighbor approach, one employing local regression analysis.
Experimental results show that the historical data collected and stored can be used to reliably forecast gas consumption. A quantitative and qualitative comparison of the two methods is discussed in details so to highlight strengths and weaknesses. Moreover, due to the peculiarity of the domain, we worked with domain subject-matter experts to understand the capability of the methods in detecting anomalous gas consumption.
Our results clearly show our forecasting techniques effectively support control room operators in identifying anomalous consumption. Providing a forecasting functionality is the first relevant step towards creating a full expert system that makes it easier for advanced operators to interpret the gas network behavior and that suggests the less-skilled ones the correct reactions to be taken upon the occurrence of anomalous events
GOLAM: A Framework for Analyzing Genomic Data
No full textThe emerging medical models aim at leveraging on high-throughput genome sequencing technologies to better target drugs to patients' personal profiles so as to increase their effectiveness. However, the huge amount of data made available by these technologies calls for sophisticated and automated analysis techniques. In this direction we present GOLAM, a framework for OLAP analysis and mining of matches between genomic regions extracted from ENCODE, a worldwide-available collection of shared genomic data. The goal of GOLAM is to overcome the current limitations of genome analysis methods, that are normally based on browsing. This is done by partially automating and speeding-up the analysis process on the one hand, by making it more flexible and introducing a multi-resolution view of data on the other. The framework has been partially implemented so far; in this paper we focus on conveying its potential and on describing its functional architecture and the underlying data models
A possible role of leaf vascular network in heat dissipation in Vitis vinifera L
Get PDFRecent studies showed how the density of lea f vascular system can be involved in the performance of physiologicalparameters. Major veins are commonly elevated in the lower epidermis of the leaf, and this anatomical feature could play asubsidiary role in increasing heat dispersion in the surrounding environment and may help dissipate excess light energy inthe leaves. The aim of this study is to analyse the role of the leaf vein network in the heat dissipation process in Vit isvinifera (L.). Major leaf veins were insulated with liquid paraffin and analysed using thermal imagi ng. A significa ntlyhigher temperature was found on the leaf tissues with insulated veins compared to untreated leaves. Further studies arerequired to assess the real contribution of the leaf vascular network in thermal dissipation
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Thermal noise and optomechanical features in the emission of a membrane-coupled compound cavity laser diode
Get PDFWe demonstrate the use of a compound optical cavity as linear displacement detector, by measuring the thermal motion of a silicon nitride suspended membrane acting as the external mirror of a near-infrared Littrow laser diode. Fluctuations in the laser optical power induced by the membrane vibrations are collected by a photodiode integrated within the laser, and then measured with a spectrum analyzer. The dynamics of the membrane driven by a piezoelectric actuator is investigated as a function of air pressure and actuator displacement in a homodyne configuration. The high Q-factor (~ 3.4 x 10^4 at 8.3x10(-3) mbar) of the fundamental mechanical mode at similar to 73 kHz guarantees a detection sensitivity high enough for direct measurement of thermal motion at room temperature (similar to 87 pm RMS). The compound cavity system here introduced can be employed as a table-top, cost-effective linear displacement detector for cavity optomechanics. Furthermore, thanks to the strong optical nonlinearities of the laser compound cavity, these systems open new perspectives in the study of non-Markovian quantum properties at the mesoscale
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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