Variable-rate speech coding: Replacing unvoiced excitations by linear prediction residues of different phonemes

Afin de réduire le débit binaire de la transmission de la parole sans perte de qualité de celle-ci, nous développons un vocodeur qui utilise des méthodes differentes pour le codage des trames voisées et non voisées. Nous présentons ici une nouvelle idée de décrire des phonèmes fricatifs (sifflantes) et plosifs avec seulement 20 bit par trame de t = 20ms. Nous montrons que ces phonèmes peuvent être représentés par des coefficients de la prédiction linéaire combinés avec un signal résiduel extrait d'un autre phonème prononcé par une personne differente connue à la station réceptrice du système de codage (voir figure 1). La présente contribution décrit aussi des algorithmes qui garantissent des transitions douces dans d'autres catégories de phonèmes. En appliquant cette technique on peut considérablement réduire le débit de transmission (jusqu'à 1 kbit/seconde) pour les trames non voisées. Nous obtenons de meilleurs résultats qu'en utilisant des variantes de CELP (prédiction linéaire excitée par une table de codage) à 4 kbit/seconde. La combinaison de ce codage avec des méthodes de codage harmonique (par exemple le MBE: 'Multiband Excitation') pour les trames voisées resulte en un débit binaire variable de moins de 3 kbit/seconde

The institutionalisation of sustainable practices in cities: how initiatives shape local selection environments

The ways in which institutions are reconfigured to change mainstream selection pressures to favour sustainability is central to research on sustainability transitions but has only recently begun to receive more attention. Of this existing work, empirical attention has mainly focused on the national level with less attention to local dynamics. Attending to this gap, we mobilise theory on institutionalisation processes and insights from the politics of transitions literature and take an actor perspective to investigate the agency of local sustainability initiatives to navigate local governance processes and reconfigure selection environments at the urban scale. Our work subsequently demonstrates the importance of diverse actor tactics, of networking for advocacy and of networking for the creation of informal, ad hoc governance arenas

Advancing urban transitions and transformations research

Urban transitions and transformations research fosters a dialogue between sustainability transitions theory an inter- and transdisciplinary research on urban change. As a field, urban transitions and transformations research encompasses plural analytical and conceptual perspectives. In doing so, this field opens up sustainability transitions research to new communities of practice in urban environments, including mayors, transnational municipal networks, and international organizations

Influence of the Metal Center in M–N–C Catalysts on the CO2 Reduction Reaction on Gas Diffusion Electrodes

In this work, the influences of various transition metal ions as active sites in high purity metal and nitrogen doped carbon catalysts in short M N C , where M Mn3 , Fe3 , Co2 , Ni2 , Cu2 , Zn2 , or Sn4 in the catalyst powders, were systematically investigated for the electrochemical reduction of CO2 in the aqueous electrolyte. The almost exclusive presence of isolated M N4 centers as catalytic sites was determined by X ray photoelectron spectroscopy XPS . The catalysts were electrochemically investigated in a gas diffusion electrode arrangement in bypass mode coupled in line to a mass spectrometer. This allowed for the nearly simultaneous detection of products and current densities in linear sweep voltammetry experiments, from which potential dependent specific production rates and faradaic efficiencies could be derived. Postmortem XPS analyses were performed after various stages of operation on the Cu N C catalyst, which was the only catalyst to produce hydrocarbons CH4 and C2H4 in significant amounts. The data provided insights into the potential induced electronic changes of the Cu N C catalyst occurring under operating conditions. Our work further experimentally revealed the high affinity of M N C catalysts to convert CO2 to industrially relevant carbonaceous raw materials, while effectively suppressing the competing hydrogen evolution reaction. These results led to a better understanding of the role of the active sites, especially the central metal ion, in M N C and could contribute significantly to the improvement of selectivities and activities for the CO2RR in this catalyst class through tailor made optimization strategie

The role of regime-level processes in closing the gap between sustainable city visions and action

There is an implementation gap between cities’ long-term sustainable visions and the short-term actions realised to achieve them. To accelerate sustainable urban transitions a greater understanding of the regime-level processes that enable or constrain translation between long-term visions and short-term action is required. Transition research to date has neglected regime processes, especially cultural-cognitive habits and heuristics, and the role of power and agency. To address this a novel analytical framework is proposed, with transition theory as the basis, additionally drawing on institutional and quasi-evolutionary theory. This framework is tested using Copenhagen as a case study, generating important insights; in particular that normative institutional processes are an effective means for regime actors to coordinate power, affect resource allocation, and impact selection pressures and adaptive capacity. The findings suggests that unless the institutional and quasi-evolutionary processes that drive action are re-configured in line with sustainable city visions then progress will be limited