1,720,965 research outputs found
VLSI decoding architectures: flexibility, robustness and performance
Full text linkStemming from previous studies on flexible LDPC decoders, this thesis work has been mainly focused on the development of flexible turbo and LDPC decoder designs, and on the narrowing of the power, area and speed gap they might present with respect to dedicated solutions. Additional studies have been carried out within the field of increased code performance and of decoder resiliency to hardware errors. The first chapter regroups several main contributions in the design and implementation of flexible channel decoders. The first part concerns the design of a Network-on-Chip (NoC) serving as an interconnection network for a partially parallel LDPC decoder. A best-fit NoC architecture is designed and a complete multi-standard turbo/LDPC decoder is designed and implemented. Every time the code is changed, the decoder must be reconfigured. A number of variables influence the duration of the reconfiguration process, starting from the involved codes down to decoder design choices. These are taken in account in the flexible decoder designed, and novel traffic reduction and optimization methods are then implemented. In the second chapter a study on the early stopping of iterations for LDPC decoders is presented. The energy expenditure of any LDPC decoder is directly linked to the iterative nature of the decoding algorithm. We propose an innovative multi-standard early stopping criterion for LDPC decoders that observes the evolution of simple metrics and relies on on-the-fly threshold computation. Its effectiveness is evaluated against existing techniques both in terms of saved iterations and, after implementation, in terms of actual energy saving. The third chapter portrays a study on the resilience of LDPC decoders under the effect of memory errors. Given that the purpose of channel decoders is to correct errors, LDPC decoders are intrinsically characterized by a certain degree of resistance to hardware faults. This characteristic, together with the soft nature of the stored values, results in LDPC decoders being affected differently according to the meaning of the wrong bits: ad-hoc error protection techniques, like the Unequal Error Protection devised in this chapter, can consequently be applied to different bits according to their significance. In the fourth chapter the serial concatenation of LDPC and turbo codes is presented. The concatenated FEC targets very high error correction capabilities, joining the performance of turbo codes at low SNR with that of LDPC codes at high SNR, and outperforming both current deep-space FEC schemes and concatenation-based FECs. A unified decoder for the concatenated scheme is subsequently propose
Effects of thermal heat treatment parameters on the properties of WE43 magnesium alloy
No full textThe WE43 is a Mg-Y-Nd alloy that presents good mechanical properties and an high creep resistance. For these reasons currently is widely used in the aerospace and automotive industries. The setting of the right thermal heat treatment parameters plays a crucial role in determine the microstructure and consequently the mechanical properties of the alloy. With this in mind, the main goal of this work has been that to identify the optimal parameters to achieve an high impact resistance and at the same time, the most suitable choice, to reach also an important cost-saving solution, which is extremely important especially from the industrial point of view
Influence of heat treatment parameters on the metallurgical quality of EN AW 7068 extruded bars
No full textSTUDIO E OTTIMIZZAZIONE DEL TRATTAMENTO TERMICO T6 PER LA LEGA 7068
Full text linkLa lega 7068 è una lega Al-Zn-Mg-Cu oggigiorno ampiamente utilizzata nei settori aeronautico ed automotive perla produzione di componenti meccanici a cui sono richieste eccellenti proprietà meccaniche. Attualmente questalega viene impiegata anche per realizzare componenti per materiale ed attrezzature specifiche per le attività diarrampicata sportiva. L’obiettivo di questo lavoro è l’ottimizzazione dei parametri del trattamento termico T6 al finedi ottenere le migliori proprietà meccaniche possibili. Lo studio ha previsto la valutazione dell’effetto di due diversitrattamenti termici T6, le cui differenze risiedono nei parametri di solubilizzazione ed invecchiamento utilizzati.E’ stata valutata l’influenza del trattamento termico sia sulla microstruttura che sulle proprietà meccaniche dialcuni campioni ottenuti attraverso un processo di estrusione. I risultati ottenuti sono stati confrontati con quellidi campioni, sempre ottenuti per estrusione, ma sottoposti solamente ad un trattamento di ricottura. Attraversol’analisi dei risultati ottenuti sono stati individuati i parametri ottimali del trattamento termico T6 adatti perconseguire una eccellente resistenza meccanica
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