179 research outputs found
Determination of phase transitions through AC conductance
No full textA cell design for AC conductance measurements at various temperatures is described. The cell does not require external spring-loaded or screwed supports, permitting the accurate identification of phase transition points irrespective of coincidental large changes in molar volume (e.g. for compounds such as AgI, TlI and organic substances showing phase-mesophase transitions
La struttura spaziale della povertà urbana: il caso milanese
No full textIl paper propone alcune riflessioni sul rapporto tra povertà urbana e variabili spaziali. La tesi sostenuta è quella che, pur al di fuori di qualsiasi determinismo ambientale, lo spazio sia un fattore determinante (per quanto non deterministico) in riferimento al tema della povertà urbana.
Nella prima parte del testo vengono presentate alcune ipotesi teoriche sul rapporto spazio-povertà. In particolare si argomenta la connessione causale tra i due termini, individuando quattro categorie micro-geografiche di concausazione della povertà urbana. Nella seconda parte del testo tali ipotesi sono messe in relazione al contesto milanese, che viene analizzato sulla base di indici da queste dedotti. La suddivisione territoriale di riferimento è quella degli 88 NIL (nuclei di identità locale) definiti dal recente Piano di Governo del Territorio; sempre dal PGT provengono i dati in riferimento alla maggior parte delle variabili spaziali utilizzate per comporre gli indici. Ciò che si ricava dall’analisi di Milano è un quadro descrittivo del disagio urbano, articolato sulla base di precise categorie spaziali, che si contrappone alla semplicistica misurazione del reddito medio dichiarato, ancorché normalizzato per il numero di componenti equivalenti
Electrochemical open circuit voltage (OCV) characterization of SOFC materials
No full textIn this paper, we are reporting an extensive characterization, by means of open circuit voltage measurements, of Ce0.8Gd0.2O2, La0.9Sr0.1Ga0.8Mg0.2O3, and La2Mo0.6W1.4O9 oxide-ions and BaCe0.8Y0.2O3 and BaCe0.55Zr0.3Y0.15O3 proton-conducting electrolyte materials for solid oxide fuel cell (SOFC) applications. This simple and common technique, well known for a long time in the electrochemical study of solid oxide fuel cells, has been here proposed for the electrical characterization of these ceramic materials, in order to define their ionic transport numbers, the maximum voltage performances, the thermal and chemical stability, and also to suggest the ideal temperature range for different applications, as in the electrochemical devices, sensors, and SOFC field. In the paper, controlled and reproducible working conditions have been applied in a wide range of temperature, by means of ultrapure gas (H2 and O2), under operational conditions found in real SOFC devices and, mainly, without the usual problems related to the chemical compatibility, the depolarization efficiency, and the high current density required to the electrode materials in the design of a more efficient SOFC device
The many shades of grey in urban governance: How illegality shapes urban planning, policy and development
No full textMost research on urban planning, policy and development only considers legal practices and actors, and treats illegal ones as insignificant anomalies, unable to structurally affect the governance of urban space. However, this approach is inadequate for explaining urban governance in contexts (e.g. several countries in the Global South, the former Soviet bloc and Southern Europe) where illegal practices such as corruption and organized crime infiltration are widespread in many public and economic sectors. This paper addresses the role of illegal actors and practices in urban governance in the Italian context, using urban regime theory as the theoretical frame of reference. The research centres on the analysis of two case studies in the city of Rome (the In-between world investigation of a criminal network that had infiltrated the local administration and shaped several urban policies, and the investigation of episodes of corruption related to the project for the new A.S. Roma soccer stadium). It shows the existence of two shades of ‘grey urban governance’: firstly, the presence of a dark urban regime, centred on a criminal organisation and parallel to the ‘regular’ one; secondly, the use of corruption as a customary practice with which real estate entrepreneurs influence municipal decisions. Overall, this research contributes to moving away from a rhetoric of ‘gentlemanly’ urban capitalism and politics, and suggests the need to revise several aspects of urban regime theory – as well as other approaches to urban governance dynamics in general – in order to incorporate the role of illegal actors and practices
The Eu1-xBa2-xCu3Oy system: oxygen content, phase transitions, point defect equilibria, and charge carriers
No full textCathode materials (NiO-LiFeO2-LiCoO2) for molten carbonate fuel cell: a diffraction, NMR and conductivity study.
No full textThe search for a NiO-based cathode for molten carbonate fuel cell has been directed towards solid solutions containing LiFeO2 and LiCoO2 in addition to nickel oxide [A. Wijayasinghe, B. Bergman, C. Lagergren, Electrochim. Acta 49 (2004) 4709.]. NiO and LiFeO2 are fully soluble in
one another, while ternary solid solutions have been previously obtained only for small (b18%) and high (N90%) LiCoO2 molar contents. The
goal of this work is to identify and characterize the compositions with the most promising electrical conductivity, which may be used as cathode
materials. We present data relative to compositions having a constant NiO/LiFeO2 molar ratio of 3:1 and a LiCoO2 content from 5 to 30 mol%
AgI-Ag oxysalt electrolytes for solid state cells
No full textAmong the family of solid electrolytes obtained from AgI and Ag oxysalts, new materials exhibiting high electric conductivity have been identified. The investigation is extended to the study of their behaviour at temperatures higher than 25degC. The product with the composition of 80 mol% AgI in the system AgI-Ag 2Cr 2O 7 performs well at 25degC; the product with the composition of 75 mol% AgI in the system AgI-Ag 2TeO 4 is the most promising at 60degC. Solid state electrolytic cells containing such materials have been discharged against various external load
Investigation of the high temperature structural behavior of La0.99Ca0.01 NbO4 proton conducting material
No full textIn this paper we report a preliminary neutron diffraction investigation of the proton conducting La0.99Ca0.01NbO4 material. Measurements have been acquired from room temperature up to 750 degrees C under dry and wet atmosphere. The main result of this investigation is the observation of the existence of a broad temperature interval where the low-T monoclinic phase coexists with the high-T tetragonal phase. Even at the highest investigated temperature small fractions of the monoclinic phase have been detected under the experimental conditions employed her
Thermoelectric power and electric conductivity of the (Ag,Na)Cl and (Ag,Na)Br solid solutions
No full textThe electric conductivity and the initial thermoelectric power are determined for the solid solutions (Ag,Na)X (X=Cl,Br) over the whole composition range. Data drawn from both kinds of measurements allow to approximately estimate the contributions of cation vacancies and interstitial Ag + to the transport process. Two composition regions are distinguished: 0les NNaXles0.6 and 0.7< NNaX<1 where interstitial Ag + and cation vacancies, respectively, are prevailin
Thermoelectric power of AgI-Ag oxysalt ionic solids
No full textThermoelectric power determinations carried out on the materials recently investigated as particularly suitable for the preparation of solid state galvanic cells allowed a comparison to be made between this family of compounds and the already studied MeAg 4I 5. The possible interest of such materials for the direct conversion of thermal energy is finally examined with respect to the p-semiconductors on the basis of an evaluation of the figure of meri
- …
