3,032 research outputs found
Methodology and optimisation of neutron-gamma pulse shape discrimination through specifically engineered scintillators coupled to Silicon Photomultipliers
No full textNuclear security has strict requirements on hand-held instrumentation. The detectors have to
be neutron sensitive, capable to discriminate between neutrons and gamma rays, possibly
providing the gamma emitter identification. Furthermore, the detecting unit has to be
compact, low power consuming and integrated into systems to perform online or near-realtime data analysis and assess the alarm level according to international standards. The thesis
reports a detailed study on factors contributing to achieving required performances with
compact detectors based on neutron sensitive scintillators coupled to Silicon Photomultipliers.
Those scintillators light time development varies with the ionising density of the interacting
particle, making possible a neutron-gamma discrimination via Pulse Shape Analysis. However,
SiPM has a sizeable intrinsic capacitance that may tamper the neutron-gamma discrimination
capability of the scintillator detector, making necessary the definition of algorithms to
guarantee the required discrimination capabilities.
Moreover, power consumption and enhanced real-time functionalities push the development
and use of Application Specific Integration Circuits (ASIC) and digital systems based on FPGA in
the abovementioned tools. In the context of two research projects with AWE and Kromek LTD,
the definition and qualification of a new approach to pulse shape discrimination with largearea Silicon Photomultipliers was applied to two newly engineered instruments
Device and method for generating random bit sequences
No full textDevice for generating random bit sequences comprising: at least one Silicon Photomultiplier sensor configured to generate a sequence of endogenous random current pulses as a result of an impact ionisation driven self-amplification of thermally generated charge carriers to which the at least one SiPM sensor can be subject; a data processing unit configured to receive said sequence of endogenous random current pulses and to determine a random bit sequence to be proved to an end-user
An assessment of the impact of possible CAP reform scenarios on Romanian agriculture
No full textUsing a simplified model, with key-variable the prices of two different possible scenarios of CAP reform after 2013 (moderate and radical), this paper present a comparison between the price effects of implementation of each reform scenario at 2015 horizon on Romanian agriculture. This short analysis shows that, under the presented hypotheses, the net welfare effect, due to the price changes, for the selected products, is positive in both reform scenarios, yet greater in the case of the radical reform. Integrated in the large context of Romanian development, it seems that the influence of CAP reform upon agriculture and rural areas will be most likely a gradual one: an interpenetration between the two scenarios is foreseeable, starting with the moderate reform that will dominate the period around 2013, the reform measures acquiring a more radical character afterwards.CAP reform, Romania, welfare effects, Agricultural and Food Policy,
Rich, Sturmian, and trapezoidal words
No full textIn this paper we explore various interconnections between rich words, Sturmian words, and trapezoidal words. Rich words, first introduced by the second and third authors together with J. Justin and S. Widmer, constitute a new class of finite and infinite words characterized by having the maximal number of palindromic factors. Every finite Sturmian word is rich, but not conversely. Trapezoidal words were first introduced by the first author in studying the behavior of the subword complexity of finite Sturmian words. Unfortunately this property does not characterize finite Sturmian words. In this note we show that the only trapezoidal palindromes are Sturmian. More generally we show that Sturmian palindromes can be characterized either in terms of their subword complexity (the trapezoidal property) or in terms of their palindromic complexity. We also obtain a similar characterization of rich palindromes in terms of a relation between palindromic complexity and subword complexity
Characterization Results for the Poset Based Representation of Topological Relations - I: Introduction and Models
No full text@article{DBLP:journals/informaticaSI/ForlizziN99,
author = {Luca Forlizzi and
Enrico Nardelli},
title = {Characterization Results for the Poset Based Representation
of Topological Relations - I: Introduction and Models.},
journal = {Informatica (Slovenia)},
volume = {23},
number = {2},
year = {1999},
bibsource = {DBLP, http://dblp.uni-trier.de}
Characterization Results for the Poset Based Representation of Topological Relations - II: Intersection and Union
No full text@article{DBLP:journals/informaticaSI/ForlizziN00,
author = {Luca Forlizzi and
Enrico Nardelli},
title = {Characterization Results for the Poset Based Representation
of Topological Relations - II: Intersection and Union.},
journal = {Informatica (Slovenia)},
volume = {24},
number = {1},
year = {2000},
bibsource = {DBLP, http://dblp.uni-trier.de}
System-on-chip Computing and Interconnection Architectures for Telecommunications and Signal Processing
No full textThis dissertation proposes novel architectures and design techniques targeting SoC building blocks for telecommunications and signal processing applications.
Hardware implementation of Low-Density Parity-Check decoders is approached at both the algorithmic and the architecture level. Low-Density Parity-Check codes are a promising coding scheme for future communication standards due to their outstanding error correction performance.
This work proposes a methodology for analyzing effects of finite precision arithmetic on error correction performance and hardware complexity. The methodology is throughout employed for co-designing the decoder. First, a low-complexity check node based on the P-output decoding principle is designed and characterized on a CMOS standard-cells library. Results demonstrate implementation loss below 0.2 dB down to BER of 10^{-8} and a saving in complexity up to 59% with respect to other works in recent literature. High-throughput and low-latency issues are addressed with modified single-phase decoding schedules. A new "memory-aware" schedule is proposed requiring down to 20% of memory with respect to the traditional two-phase flooding decoding. Additionally, throughput is doubled and logic complexity reduced of 12%. These advantages are traded-off with error correction performance, thus making the solution attractive only for long codes, as those adopted in the DVB-S2 standard. The "layered decoding" principle is extended to those codes not specifically conceived for this technique. Proposed architectures exhibit complexity savings in the order of 40% for both area and power consumption figures, while implementation loss is smaller than 0.05 dB.
Most modern communication standards employ Orthogonal Frequency Division Multiplexing as part of their physical layer. The core of OFDM is the Fast Fourier Transform and its inverse in charge of symbols (de)modulation. Requirements on throughput and energy efficiency call for FFT hardware implementation, while ubiquity of FFT suggests the design of parametric, re-configurable and re-usable IP hardware macrocells. In this context, this thesis describes an FFT/IFFT core compiler particularly suited for implementation of OFDM communication systems. The tool employs an accuracy-driven configuration engine which automatically profiles the internal arithmetic and generates a core with minimum operands bit-width and thus minimum circuit complexity. The engine performs a closed-loop optimization over three different internal arithmetic models (fixed-point, block floating-point and convergent block floating-point) using the numerical accuracy budget given by the user as a reference point. The flexibility and re-usability of the proposed macrocell are illustrated through several case studies which encompass all current state-of-the-art OFDM communications standards (WLAN, WMAN, xDSL, DVB-T/H, DAB and UWB). Implementations results are presented for two deep sub-micron standard-cells libraries (65 and 90 nm) and commercially available FPGA devices. Compared with other FFT core compilers, the proposed environment produces macrocells with lower circuit complexity and same system level performance (throughput, transform size and numerical accuracy).
The final part of this dissertation focuses on the Network-on-Chip design paradigm whose goal is building scalable communication infrastructures connecting hundreds of core. A low-complexity link architecture for mesochronous on-chip communication is discussed. The link enables skew constraint looseness in the clock tree synthesis, frequency speed-up, power consumption reduction and faster back-end turnarounds. The proposed architecture reaches a maximum clock frequency of 1 GHz on 65 nm low-leakage CMOS standard-cells library. In a complex test case with a full-blown NoC infrastructure, the link overhead is only 3% of chip area and 0.5% of leakage power consumption.
Finally, a new methodology, named metacoding, is proposed. Metacoding generates correct-by-construction technology independent RTL codebases for NoC building blocks. The RTL coding phase is abstracted and modeled with an Object Oriented framework, integrated within a commercial tool for IP packaging (Synopsys CoreTools suite). Compared with traditional coding styles based on pre-processor directives, metacoding produces 65% smaller codebases and reduces the configurations to verify up to three orders of magnitude
Measuring Nonclassicality of Mesoscopic Twin-Beam States with Silicon Photomultipliers
No full textThe study of nonclassical properties of quantum states is a relevant topic for fundamental Quantum Optics and Quantum Information applications. In the mesoscopic domain, promising results have been obtained using photon-number-resolving detectors. Here we show recent results achieved with the class of Silicon Photomultipliers: by a proper analysis of the output signal, the nonclassicality of twin-beam states can be detected and exploited
Qualification and performance of a neutron detector system with enhanced gamma discrimination, based on Silicon Photomultiplier arrays coupled to an EJ-299-34 scintillator
No full textSilicon Photomultipliers (SiPM) are a new class of photon sensors featuring high detection efficiency, single photon sensitivity and extended dynamic range; they represent a valuable solution for compact, lightweight hand-held instruments, possibly battery operated. This paper reports the studies performed with an array of 16 SiPM coupled to a novel plastic scintillator sensitive to fast neutrons with gamma discrimination, a proof-of-concept towards the development of instruments for border control against the illicit trafficking of radioactive material. The array of SiPM provides 16 individual outputs but, in this application, a single signal proportional to the total amount of light seen by the sensor is required. Two different Front-End EIectronics (FEE) circuits to sum the analogue signals have been considered and compared. The comparison has been based on the impact of the FEE on the neutron-gamma discrimination capability, based on on Pulse Shape Discrimination (PSD) algorithms. The optimal configuration has been shown to provide a Figure of Merit (FoM) of 2.56±0.0I in the energy window of 1 - I.5~mathrm Mmathrm emathrm V, confirming the state-of-the-art performance of this solution
Impact of the Detected Scintillation Light Intensity on Neutron-Gamma Discrimination
No full textThis article reports the method and the results of a study on the impact of the detected light intensity on gamma-neutron discrimination. In particular, the minimum number of photons required to achieve a statistically significant separation was measured and shown to be stable against a variation of the photon detection efficiency (PDE) of the system under study. The method, developed using an EJ-276 scintillator bar coupled to a silicon photomultiplier (SiPM), is of general interest. For this specific system, the minimum statistic was measured to be 317 +/- 16 photons, corresponding to different values of the deposited energy, as the PDE was changed
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