Od žab k ribi

This paper traces the development of "the big-fish-little-pond" effect (BFLPE), which asserts that students in high-ability classes and schools have lower academic self-concepts than their equally able counterparts in low- and mixed-ability environments. The paper begins with a description of the problem outlined in the BFLPE model and continues by examining early BFLPE research and by tracing advances in the field. Criticisms of the BFLPE are outlined and research is described that addresses these criticisms. The paper concludes by presenting suggestions for future BFLPE studies.V prispevku je predstavljen razvoj učinka "velike ribe v majhnem ribniku" (ang. Big- Fish-Little-Pond-Effect), ki ugotavlja, da imajo učenci v oddelkih na najvišjem nivoju nižjo učno samopodobo kot njihovi enako sposobni vrstniki v oddelkih na nižjih nivojih in heterogenih oddelkih. Uvodoma je v prispevku opisan izpostavljeni problem BFLPE modela, nato pa doprinosi na področju njegovega zgodnjega raziskovanja. Na osnovi raziskovalnih spoznanj je predstavljena tudi kritika BFLPE modela ter smernice oziroma predlogi za raziskovanje obravnavanega učinka v prihodnje

Anhydrous phosphoric acid functionalized sintered mesoporous silica nanocomposite proton exchange membranes for fuel cells

A novel inorganic proton exchange membrane based on phosphoric acid (PA)-functionalized sintered mesoporous silica, PA-meso-silica, has been developed and investigated. After sintering at 650 °C, the meso-silica powder forms a dense membrane with a robust and ordered mesoporous structure, which is critical for retention of PA and water within the porous material. The PA-meso-silica membrane achieved a high proton conductivity of 5 × 10–3 to 5 × 10–2 S cm–1 in a temperature range of 80–220 °C, which is between 1 and 2 orders of magnitudes higher than a typical membrane Nafion 117 or polybenzimidazole (PBI)/PA in the absence of external humidification. Furthermore, the PA-meso-silica membranes exhibited good chemical stability along with high performance at elevated temperatures, producing a peak power density of 632 mW cm–2 using a H2 fuel at 190 °C in the absence of external humidification. The high membrane proton conductivity and excellent fuel cell performance demonstrate the utility of PA-meso-silica as a new class of inorganic proton exchange membranes for use in the high-temperature proton exchange membrane fuel cells (PEMFCs)

Porous Inorganic Membranes for CO 2

INGENIERIE+MP