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Nell’ultimo ventennio, un numero importante di lavori sono stati consacrati allo studio della rappresentazione dello spazio nei testi letterari. Tale interesse sembra inscriversi sia nell’evoluzione dei generi, caratterizzati da una spazializzazione crescente delle forme narrative, sia nello sviluppo di pratiche artistiche legate alla creazione di carte letterarie. In seguito all’affermarsi dello spatial turn negli studi letterari e culturali, parte della critica ha focalizzato la sua attenzione sulla relazione che intercorre tra spazio immaginario, spazio referenziale e pratica cartografica. Quest’ultimo aspetto costituisce uno dei temi più interessanti della metodologia geocritica. Il presente articolo mira a studiare questa “convergenza” tra la letteratura e la cartografia, con l’intento di esaminare la testualità delle carte letterarie e, in particolare, la loro dimensione retorica. Le carte letterarie sono in grado di rappresentare i luoghi in cui si svolge l’azione di un romanzo, o di più romanzi, permettendo allo scrittore di costruire un mondo immaginario che i lettori esplorano assieme ai personaggi.

Il romanzo noir italiano ha iniziato ad imporsi all’inizio degli anni novanta e si è conquistato, nei due decenni successivi, uno spazio senza precedenti sia nelle librerie che nella discussione mediatica. Molti autori, nel corso degli anni, si sono sempre più affermati. Un caso emblematico è rappresentato dallo scrittore Massimo Carlotto. Vittima di uno dei casi più controversi della storia politica italiana, Massimo Carlotto usa il romanzo noir come sostituto della ricerca giudiziaria, sulla base degli atti processuali dei casi già passati in giudicato. Nei suoi romanzi troviamo mescolati discorso politico e discorso sociale, oltre ad una rappresentazione della società fortemente distopica: avvocati, giudici, poliziotti, imprenditori e amministratori pubblici corrotti. Il presente articolo propone un’analisi del romanzo Arriverderci, amore ciao, pubblicato nel 2001. Protagonista del romanzo è Giorgio Pellegrini, fuggiasco, criminale e narratore, esempio perfetto di un criminale in ascesa e integrato socialmente. Ancora una volta, lo scrittore padovano sceglie di ambientare le sue storie nel ricco Nord-est italiano, con l’intento di denunciare la collusione tra istituzioni politiche, giudiziarie e i grandi investitori locali.

We present a review of the basic operating principles and measurement schemes of standalone and hybrid distributed optical fiber sensors based on Raman and Brillouin scattering phenomena. Such sensors have been attracting a great deal of attention due to the wide industrial applications they offer, ranging from energy to oil and gas, transportation and structural health monitoring. In distributed sensors, the optical fiber itself acts as a sensing element providing unique measurement capabilities in terms of sensing distance, spatial resolution and number of sensing points. The most common configuration exploits optical time domain reflectometry, in which optical pulses are sent along the sensing fiber and the backscattered light is detected and processed to extract physical parameters affecting its intensity, frequency, phase, polarization or spectral content. Raman and Brillouin scattering effects allow the distributed measurement of temperature and strain over tens of kilometers with meter-scale spatial resolution. The measurement is immune to electromagnetic interference, suitable for harsh environments and highly attractive whenever large industrial plants and infrastructures have to be continuously monitored to prevent critical events such as leakages in pipelines, fire in tunnels as well as structural problems in large infrastructures like bridges and rail tracks. We discuss the basic sensing mechanisms based on Raman and Brillouin scattering effects used in distributed measurements, followed by configurations commonly used in optical fiber sensors. Hybrid configurations which combine Raman and Brillouin-based sensing for simultaneous strain and temperature measurements over the same fiber using shared resources will also be addressed. We will also discuss advanced techniques based on pulse coding used to overcome the tradeoff between sensing distance and spatial resolution affecting both types of sensors, thereby allowing measurements over tens of kilometers with meter-scale spatial resolution, and address recent advances in measurement schemes employing the two scattering phenomena.

We propose and experimentally demonstrate the use of cyclic pulse coding for enhanced performance in distributed acoustic sensing based on a phase-sensitive optical time-domain reflectometry (φ-OTDR) using direct detection. First, we present a theoretical analysis showing that to make cyclic pulse coding effective in φ-OTDR, the laser linewidth and stability must be optimized to simultaneously guarantee intrapulse coherence and interpulse incoherence. We then confirm that commercial off-the-shelf distributed feedback (DFB) lasers can satisfy these conditions, providing coding gain consistent with theoretical predictions. By externally modulating such lasers with cyclic pulse coding, we demonstrate a distributed acoustic sensor capable of measuring vibrations of up to 500 Hz over 5 km of standard single-mode fiber with 5-m spatial resolution with ~9-dB signal-to-noise ratio (SNR) improvement compared with the single-pulse equivalent. We also show that the proposed solution offers sensing performances that are comparable to similar sensors employing highly coherent and stabilized external cavity lasers and a single-pulse φ-OTDR.

We describe a fiber-optic system to measure the liquid level inside a container. The technique is based on the extraction of the temperature profile of the fiber by using a fiber Bragg grating (FBG) array. When the temperatures of the liquid and the gas are different, the liquid level can be estimated. We present a physical model of the system and the experimental results and we compare different algorithms to extract the liquid level from the temperature profile. We also show how air convection influences the temperature profile and the level of estimation accuracy. We finally show dynamic response measurements which are used to obtain the response time of the sensor. Turbomachinery monitoring is proposed as one possible application of the device.

The behaviour of distributed temperature sensors based on spontaneous Raman scattering and coded OTDR (optical time domain reflectometry) is studied both theoretically and experimentally; in particular a high performance scheme has been implemented using amplitude modulation according to Simplex coding, direct detection and additional use of lumped Raman amplification to further extend the sensing range. An efficient and cost-effective distributed temperature sensing system operating along 30 km of dispersion-shifted fibre with 17 m spatial resolution and 5 K temperature resolution is theoretically demonstrated and experimentally achieved using 255 bit Simplex coding and low-power commercially available laser diodes (80 mW CW power). Use of lumped Raman amplification to produce high-power coded pulses allows further 10 km distance enhancement, resulting in a total measurement range of 40 km. [ABSTRACT FROM AUTHOR]

An investigation is performed of the possibility of achieving simultaneous distributed strain and temperature sensing based on hybrid Raman-Brillouin scattering with the use of multi-wavelength optical sources such as common Fabry-Perot (FP) lasers. By employing a self-heterodyne detection scheme based on a multi-wavelength optical local oscillator, the benefits of FP lasers are fully exploited, allowing for high-power Raman intensity measurements and a simultaneous high-accuracy detection of the Brillouin frequency shift parameter for each FP longitudinal mode. Experimental results point out a significant reduction of coherent Rayleigh noise, and highlight the enhanced performance in hybrid Raman-Brillouin sensing when using FP lasers; in particular using standard FP lasers at 1550 nm results in about 12 dB (7 dB) temperature (strain) accuracy improvement at 25 km sensing distance with respect to the use of standard distributed feedback lasers. [ABSTRACT FROM AUTHOR]

In this paper we describe and implement a long-range Brillouin optical time-domain analysis (BOTDA) sensor, for both temperature and strain measurements, using optical pulse coding techniques. A theoretical analysis of Simplex coding applied to BOTDA systems is presented and experimentally demonstrated for both Brillouin loss and Brillouin gain configurations. With the proposed technique, [?]7.1 dB and [?]10.3 dB of signal-to-noise ratio improvements are demonstrated in BOTDA measurements using 127-bit and 511-bit Simplex codes, respectively. This feature allows us to extend the dynamic range of the measurements, overcoming the limitations to the maximum usable optical power imposed by pump depletion and modulation instability; thus, the sensing range can be extended by several tens of kilometers while keeping meter-scale spatial resolution. Experimental results show the capabilities of optical pulse coding techniques to achieve 1 m spatial resolution over 50 km of standard single-mode fiber enabling temperature and strain resolutions equal to 2.2 degC and 44 ue, respectively. [ABSTRACT FROM AUTHOR]