20 research outputs found
SOAs and Digital Linearization in Optical Networks-A Stochastic Investigation
No full textDigital predistortion has recently spurred interest in photonics. In this paper, the authors perform a sensitivity analysis of three digital predistortion algorithms and demonstrate an increase in performance and, in some cases, robustness to uncertainties
Energy Detection based Blind Synchronization for Pulse Shape Modulated IR-UWB Systems
No full textInternational audienceSynchronization is a key performance-limiting factor in any communication system and a challenging task to accomplish. In this paper, an energy detection based non dataaided (NDA) algorithm for orthogonal pulse shape modulated (PSM) impulse radio ultra wideband (IR-UWB) system is proposed. Relying on unique signal structure, simple overlap-add operation followed by energy detection enables synchronization. The algorithm remains functional under practical scenarios i.e. in the presence of inter-frame and inter-symbol interference (IFI & ISI) and with M-ary modulation. Simulation results are provided to demonstrate the performance of proposed algorithm
A complete receiver solution for a chaotic direct sequence spread spectrum communication system
No full textAbstract — This paper is devoted to receiver design in a Chaotic Direct-Sequence Spread Spectrum (CD3S) digital communication system. The demodulation is achieved through chaos synchronization in an efficient manner thanks to dual Unscented Kalman Filtering. The problem of carrier phase recovery, frequently neglected in chaos-based communication systems, is addressed either through Costas loop prior to demodulation or by dual estimation of the code, symbol and phase in baseband. The input signal power fluctuations, which often causes large errors in synchronizing chaotic waveforms, is also taken into account. Numerical simulations are provided to show the significance of the proposed receiver for both Additive White Gaussian Noise (AWGN) channel and a nonstationary channel. I
Heterozygous loss-of-function SEC61A1 mutations cause autosomal-dominant tubulo-interstitial and glomerulocystic kidney disease with anemia
No full textAutosomal-dominant tubulo-interstitial kidney disease (ADTKD) encompasses a group of disorders characterized by renal tubular and interstitial abnormalities, leading to slow progressive loss of kidney function requiring dialysis and kidney transplantation. Mutations in UMOD, MUC1, and REN are responsible for many, but not all, cases of ADTKD. We report on two families with ADTKD and congenital anemia accompanied by either intrauterine growth retardation or neutropenia. Ultrasound and kidney biopsy revealed small dysplastic kidneys with cysts and tubular atrophy with secondary glomerular sclerosis, respectively. Exclusion of known ADTKD genes coupled with linkage analysis, whole-exome sequencing, and targeted re-sequencing identified heterozygous missense variants in SEC61A1-c.553A>G (p.Thr185Ala) and c.200T > G (p.Val67Gly)-both affecting functionally important and conserved residues in SEC61. Both transiently expressed SEC6A1A variants are delocalized to the Golgi, a finding confirmed in a renal biopsy from an affected individual. Suppression or CRISPR-mediated deletions of sec61al2 in zebrafish embryos induced convolution defects of the pronephric tubules but not the pronephric ducts, consistent with the tubular atrophy observed in the affected individuals. Human mRNA encoding either of the two pathogenic alleles failed to rescue this phenotype as opposed to a complete rescue by human wild-type mRNA. Taken together, these findings provide a mechanism by which mutations in SEC61A1 lead to an autosomal-dominant syndromic form of progressive chronic kidney disease. We highlight protein translocation defects across the endoplasmic reticulum membrane, the principal role of the SEC61 complex, as a contributory pathogenic mechanism for ADTKD
Reação de progênies de maracujazeiro-azedo à antracnose.
No full textO presente trabalho foi desenvolvido em casa-de-vegetação, na Estação Biológica da Universidade de Brasilia, e teve como O presente objetivo avaliar a reação de progênies de maracujazeiro-azedo ao fungo Colletotrichum gloeosporioides (Penzig) Saccardo, agente causal da antracnose, com base na severidade (escala de notas) e incidência (% de plantas atacadas) da doença. azou-se o delineamento de blocos casualizados, com quatro repetições e seis plantas por parcelas, em esquema Utilizou-se parcela subdividida, sendo sete épocas de avaliação na parcela e 72 progênies na subparcela. O fungo C. gloeosporioides inoculado nas progênies de maracujazeiro-azedo, no estágio de mudas, na concentração 5x10º, por aspersão da suspensão sobre ferimentos pré-estabelecidos com auxílio de escova de aço de cerdas finas. Foram realizadas sete avaliações, a primeira aos 20 dias após a inoculação e as demais, em intervalos a cada sete dias. Para avaliar o grau de incidência e severidade da antracnose, estabeleceu-se uma escala de notas de 1 a 7, sendo 1 = ausência de sintomas; 2 = de 1 a 10% da área lesada atingida; 3 = de 10 a 25% da área lesada atingida; 4 = de 25 a 50% da área lesada atingida; 5 = de 50 a 100% da área lesada atingida; 6 = rompimento do tecido necrosado e 7 = desfolha. Consideraram-se como Resistentes (R) as plantas com notas médias d" 2; Moderadamente Resistentes (MR) as plantas com notas médias > 2 e d" 3; Suscetíveis (S) as plantas com notas médias > 3 e d" 4; e Altamente Suscetiveis (AS) as plantas com notas médias > 4. progênies mostraram diferenças significativas quanto à incidência de C. gloeosporioides ao longo das sete avaliações. O mesmo não ocorreu com respeito à severidade. No geral, duas progênies foram classificadas como Moderadamente Resistentes; oito como suscetíveis e 62 como Altamente Suscetiveis. Houve correlação da média de severidade com incidência da antracnose, demonstrando a relação entre os dois parâmetros e a confiabilidade de ambos
Robustness Improvement of Compact Predistorters in a CO-OFDM System Using Semiconductor Optical Amplifiers
No full textInternational audienceThis paper focuses on digital signal processing techniques compensating the non-linear effects inherent to optical modulation or amplification within a coherent optical orthogonal frequency division multiplexing (CO-OFDM) transmitter featuring a semiconductor optical amplifier (SOA). Two complementary approaches are specifically considered: crest factor reduction and linearization using a digital baseband predistortion. Two possible implementations are presented for the digital predistortion block. One is the basic solution of static compensation; the other consists in a parallel two-box digital polynomial predistorter (PTB) combining, in parallel, a static nonlinear block with a memory polynomial predistorter. Moreover, we show that a linearization of the dynamic behavior of the transmitter, in addition to peak-to-average power ratio (PAPR) reduction, offers better performance. The robustness of the predistorters or of the combined predistorter/PAPR reduction blocks is assessed for various scenarios. Finally, we propose solutions to improve robustness via multipoint identification or switching strategies for predistortion
COMPARISON BETWEEN THE BEHAVIOR OF PURE AND COMMERCIAL UNSTABLE AUSTENITIC STAINLESS STEELS IN THE PRESENCE OF HYDROGEN
No full textRobustness analysis of a parallel two-box digital polynomial predistorter for an SOA-based CO-OFDM system
No full textInternational audienceThe linearization performance of various digital baseband pre-distortion schemes is evaluated in this paper for a coherent optical OFDM (CO-OFDM) transmitter employing a semiconductor optical amplif er (SOA). In particular, the benef ts of using a parallel two-box (PTB) behavioral model, combining a static nonlinear function with a memory polynomial (MP) model, is investigated for mitigating the system nonlinearities and compared to the memoryless and MP models. Moreover, the robustness of the predistorters under different operating conditions and system uncertainties is assessed based on a precise SOA physical model. The PTB scheme proves to be the most effective linearization technique for the considered setup, with an excellent performance-complexity tradeoff over a wide range of conditions
Tensor-network-based predistorter design for multiple-input multiple-output nonlinear systems
No full textThe recent development in tensor algorithms has shed new light on many design problems previously doomed by the curse of dimensionality. In particular, latest advances are seen in the tensor-network-based multiple-input multiple-output (MIMO) Volterra series modeling of nonlinear systems whereby the Volterra kernels can now be efficiently identified at an unprecedented order and memory length. Subsequent to nonlinear system identification, this paper studies the nonlinear MIMO predistorter design that is crucial for linearizing the response of nonlinear modules such as power amplifiers in mixed-signal applications. Two tensor-network-based predistorter design schemes are presented for the first time, whose effectiveness are validated through practical examples
