Techniques émergentes de codage espace-temps pour les systèmes de communications optiques

Research in the field of optical fiber communications is advancing at a rapid pace in order to meet the growing needs for higher data rates. The main driving forces behind these advancements are the availability of multiple degrees of freedom in the optical fiber allowing for multiplexing more data: amplitude, phase and polarization state of the optical field, along with time and wavelength are already used in the deployed optical transmission systems. Yet, these systems are approaching their theoretical capacity limits and an extra dimension "space" is investigated to achieve the next capacity leap. However, packing several data channels in the same medium brings with it differential impairments and crosstalk that can seriously deteriorate the performance of the system. In this thesis, we focus on recent optical MIMO schemes based on polarization division multiplexing (PDM) and space division multiplexing (SDM). In both, we assess the performance penalties induced by non-unitary crosstalk and loss disparities among the channels arising from imperfections in the used optical components (fibers, amplifiers, multiplexers...), and suggest novel MIMO coding techniques known as Space-Time (ST) codes, initially designed for wireless multi-antenna channels, to mitigate them.La recherche dans le domaine des communications sur fibres optiques avance à un rythme rapide afin de satisfaire des demandes croissantes de communications à débits élevés. Les principaux moteurs de ces avancements sont la multitude de degrés de liberté offerts par la fibre permettant ainsi la transmission de plus de données: l'amplitude, la phase et l'état de polarisation du champ optique, ainsi que le temps et la longueur d'onde sont déjà utilisés dans les systèmes de transmission optique déployés. Pourtant, ces systèmes s'approchent de leur limite fondamentale de capacité et un degré supplémentaire: "la dimension spatiale" est étudié pour réaliser un saut qualitatif majeur en termes de capacité de transmission. Cependant, l'insertion de plusieurs flux de données dans le même canal de propagation induit également des pertes différentielles et de la diaphonie entre les flux, ce qui peut fortement réduire la qualité du système de transmission. Dans cette thèse, nous nous concentrons sur les systèmes de transmission optique de type MIMO basés sur un multiplexage en polarisation ou en modes de propagation. Dans les deux cas, nous évaluons la dégradation de la performance provoquée par une interférence inter-canaux non-unitaire et des disparités de gain entre les canaux engendrées par des imperfections dans les composants optiques utilisés (fibres, amplificateurs, multiplexeurs...), et proposons pour les combattre, de nouvelles techniques de codage pour les systèmes MIMO nommées "codes Spatio-Temporels" (ST), préalablement conçues pour les systèmes radios multi-antennaires

Design and implementation of alow complexity NCO based CFO compensation unit

PeerReviewe

Charter School Funding: Inequity’s Next Frontier

Of all the controversies swirling around the nation’s charter schools, none is more hotly contested than the debate over funding. Charter opponents charge that] these autonomous public schools are draining scarce resources from public school districts. Proponents, by contrast, complain that charter schools do not get their fair share of public education dollars

City of Meridian v. Petra Inc. Clerk\u27s Record v. 2 Dckt. 39006

https://digitalcommons.law.uidaho.edu/idaho_supreme_court_record_briefs/4732/thumbnail.jp

Water electrolysis: from textbook knowledge to the latest scientific strategies and industrial developments

International audienceReplacing fossil fuels with energy sources and carriers that are sustainable, environmentally benign, and affordable is amongst the most pressing challenges for future socio-economic development. To that goal, hydrogen is presumed to be the most promising energy carrier. Electrocatalytic water splitting, if driven by green electricity, would provide hydrogen with minimal CO2 footprint. The viability of water electrolysis still hinges on the availability of durable earth-abundant electrocatalyst materials and the overall process efficiency. This review spans from the fundamentals of electrocatalytically initiated water splitting to the very latest scientific findings from university and institutional research, also covering specifications and special features of the current industrial processes and those processes currently being tested in large-scale applications. Recently developed strategies are described for the optimisation and discovery of active and durable materials for electrodes that ever-increasingly harness first-principles calculations and machine learning. In addition, a technoeconomic analysis of water electrolysis is included that allows an assessment of the extent to which a large-scale implementation of water splitting can help to combat climate change. This review article is intended to cross-pollinate and strengthen efforts from fundamental understanding to technical implementation and to improve the ‘junctions’ between the field's physical chemists, materials scientists and engineers, as well as stimulate much-needed exchange among these groups on challenges encountered in the different domains

Assuming Data Integrity and Empirical Evidence to The Contrary

Background: Not all respondents to surveys apply their minds or understand the posed questions, and as such provide answers which lack coherence, and this threatens the integrity of the research. Casual inspection and limited research of the 10-item Big Five Inventory (BFI-10), included in the dataset of the World Values Survey (WVS), suggested that random responses may be common. Objective: To specify the percentage of cases in the BRI-10 which include incoherent or contradictory responses and to test the extent to which the removal of these cases will improve the quality of the dataset. Method: The WVS data on the BFI-10, measuring the Big Five Personality (B5P), in South Africa (N=3 531), was used. Incoherent or contradictory responses were removed. Then the cases from the cleaned-up dataset were analysed for their theoretical validity. Results: Only 1 612 (45.7%) cases were identified as not including incoherent or contradictory responses. The cleaned-up data did not mirror the B5P- structure, as was envisaged. The test for common method bias was negative. Conclusion: In most cases the responses were incoherent. Cleaning up the data did not improve the psychometric properties of the BFI-10. This raises concerns about the quality of the WVS data, the BFI-10, and the universality of B5P-theory. Given these results, it would be unwise to use the BFI-10 in South Africa. Researchers are alerted to do a proper assessment of the psychometric properties of instruments before they use it, particularly in a cross-cultural setting

Leading Towards Voice and Innovation: The Role of Psychological Contract

Background: Empirical evidence generally suggests that psychological contract breach (PCB) leads to negative outcomes. However, some literature argues that, occasionally, PCB leads to positive outcomes. Aim: To empirically determine when these positive outcomes occur, focusing on the role of psychological contract (PC) and leadership style (LS), and outcomes such as employ voice (EV) and innovative work behaviour (IWB). Method: A cross-sectional survey design was adopted, using reputable questionnaires on PC, PCB, EV, IWB, and leadership styles. Correlation analyses were used to test direct links within the model, while regression analyses were used to test for the moderation effects. Results: Data with acceptable psychometric properties were collected from 11 organisations (N=620). The results revealed that PCB does not lead to substantial changes in IWB. PCB correlated positively with prohibitive EV, but did not influence promotive EV, which was a significant driver of IWB. Leadership styles were weak predictors of EV and IWB, and LS only partially moderated the PCB-EV relationship. Conclusion: PCB did not lead to positive outcomes. Neither did LS influencing the relationships between PCB and EV or IWB. Further, LS only partially influenced the relationships between variables, and not in a manner which positively influence IWB