2,979 research outputs found
MoM Computation of Losses of an Array of Parallel Magnetic and Conductive Wires in a Transverse Magneto-quasi-static Field
No full textA Trefftz-like method is proposed for the evaluation of losses in an array of parallel magnetic and conductive wires subject to an external time-harmonic magneto-quasi-static field. The formulation is tested on a two-dimensional model of a submarine three-core power cable armor. The accuracy of the method is verified by comparison with a reference Finite Element Method solutio
An Integral Formulation for an Array of Wires in a 3-D Magneto-Quasi-Static Field
No full textThere are many applications in which it is required to compute quasi-stationary magnetic fields and related quantities in possibly large regions containing many magnetic and/or conductive thin wires. When analyzing these problems by the finite-element method, one has to discretize the wires into fine elements in order to resolve the skin effect and the space separating the wires. Heavy computational burden is, therefore, needed to solve the resulting equations. To overcome such limitations, we propose a magnetic field integral formulation in the magneto-quasi-static regime that is suitable for computing the magnetic field in a 3-D domain in the presence of thin wires. To reduce the computational complexity, the wires are treated as 1-D manifolds embedded in the surrounding 3-D space. To validate the proposed methodology, we compare the cost and accuracy of our approach to full scale finite-element simulations of an array of wires in a 3-D external magneto-quasi-static field
Computation of Armor Losses in AC Submarine Cables
No full textWe propose an innovative fast 3D approach for the accurate computation of electromagnetic losses in the metallic armors of submarine cables. In order to develop a scheme that is more efficient with respect to most commonly used 3D simulation methods, typically based on the Finite Element Method (FEM), we proceed by proposing a suitable discretization of an integral formulation. In the proposed approach, each wire of the armor is modeled as filamentary which leads to a dramatic reduction in the number of degrees of freedom in the numerical model and in the overall computational burden. The new approach can be applied to cables where armor wires are stranded either with opposite (contralay) or same (equilay) orientation as the central phase cables. The efficiency of the proposed method is especially notable in latter case for which FEM is very demanding due to the extremely large model size. The reduction in both computation times and memory footprint allow performing extensive sensitivity studies with respect to geometrical parameters and material properties that would be otherwise unaffordable with existing 3D methods
Fully Coupled Computation of Losses in Metallic Sheaths and Armor of AC Submarine Cables
No full textThe problem of computing in an efficient and accurate way the armor losses in three-core AC submarine cables has been of great interest to the offshore cable community for some years. Indeed, efficiency of the computation method is crucial to allow comprehensive parametric analysis as might be needed in the design study. In [1] an algorithm based on integral equations for performing such calculations with an accuracy comparable (within acceptable tolerances) to state-ofthe- art Finite Element Method (FEM) approaches was presented. In the present study, we extend the above mentioned algorithm to account for the mutual inductive coupling between armor wires and metallic screens, which are often present in actual cables structure. We show that the most notable properties of the original algorithm are preserved in this coupled formulation. In particular we discuss how exploiting the cable structure periodicity and symmetry leads to huge computational cost reductions. The new extended simulation tool is applied to a parametric study to assess how geometry and material properties influence losses and to assess in particular the impact of the metallic sheaths
Integral Formulation for Losses Computation in Tripolar Submarine Cables with Shield Wires, Moisture Barriers and Armor
No full textMethod-of-Moments (MoM) is coupled with PEEC in order to compute Joule and hystheresis losses in the armor, shields and moisture barriers of a submarine tripolar cable. The large size and complex structure of the linear algebraic system resulting from the problem discretization demands for a suitably tailored solver. We describe a block-Gauß-Seidel preconditioner for Krylov subspace methods that allows for a matrix-free solver implementation, resulting in a dramatic reduction of computation time and memory requirements w.r.t. other brute-force modeling approaches
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
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