Romanian Academy

About: Romanian Academy is a archive organization based out in Bucharest, Romania. It is known for research contribution in the topics: Population & Nonlinear system. The organization has 3662 authors who have published 10491 publications receiving 146447 citations. The organization is also known as: Academia Română & Societatea Literară Română.

Tailoring mixed ionic–electronic conduction in H2 permeable membranes based on the system Nd5.5W1−xMoxO11.25−δ

Abstract: Lanthanide tungstates (Ln6WO12) are promising candidates for the development of ceramic hydrogen transport membranes since they exhibit mixed ionic (proton and oxygen ion transport) and electronic conductivity and remarkable stability in a moist CO2 environment at high temperatures. This work presents the structural and electrochemical characterization of mixed conducting materials for the specific system Nd5.5W1−xMoxO11.25−δ (x = 0, 0.1, 0.5 and 1). Evolution of the crystalline structure is studied as a function of the sintering temperature. Shrinkage behavior is analyzed for all compositions in the temperature range from 1000 °C to 1500 °C and these compounds show high sintering activity even at relatively low temperatures. The total conductivity in different environments is studied systematically for samples sintered at 1350 °C. The H/D isotopic effect is also studied by DC-electrochemical measurements. H2 permeation is investigated for the selected compound Nd5.5W0.5Mo0.5O11.25−δ in the range of 700–1000 °C achieving values of 0.3 mL min−1 cm−2 for a 0.9 mm thick disc membrane. Finally, the stability of this material under different CO2 and H2S-rich atmospheres at high temperatures is proven.

Assessing the spatial variability of coefficients of landslide predictors in different regions of Romania using logistic regression

Abstract: . In landslide susceptibility assessment, an important issue is the correct identification of significant contributing factors, which leads to the improvement of predictions regarding this type of geomorphologic processes. In the scientific literature, different weightings are assigned to these factors, but contain large variations. This study aims to identify the spatial variability and range of variation for the coefficients of landslide predictors in different geographical conditions. Four sectors of 15 km × 15 km (225 km2) were selected for analysis from representative regions in Romania in terms of spatial extent of landslides, situated both on the hilly areas (the Transylvanian Plateau and Moldavian Plateau) and lower mountain region (Subcarpathians). The following factors were taken into consideration: elevation, slope angle, slope height, terrain curvature (mean, plan and profile), distance from drainage network, slope aspect, land use, and lithology. For each sector, landslide inventory, digital elevation model and thematic layers of the mentioned predictors were achieved and integrated in a georeferenced environment. The logistic regression was applied separately for the four study sectors as the statistical method for assessing terrain landsliding susceptibility. Maps of landslide susceptibility were produced, the values of which were classified by using the natural breaks method (Jenks). The accuracy of the logistic regression outcomes was evaluated using the ROC (receiver operating characteristic) curve and AUC (area under the curve) parameter, which show values between 0.852 and 0.922 for training samples, and between 0.851 and 0.940 for validation samples. The values of coefficients are generally confined within the limits specified by the scientific literature. In each sector, landslide susceptibility is essentially related to some specific predictors, such as the slope angle, land use, slope height, and lithology. The study points out that the coefficients assigned to the landslide predictors through logistic regression are capable to reveal some important characteristics in landslide manifestation. The study also shows that the logistic regression could be an alternative method to the current Romanian methodology for landslide susceptibility and hazard mapping.