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To develop a simple model to predict the glass cracking andlor breaking, radiant heating tests were carried out on float glass and wired glass. By changing the imposed heat flux and lateral restraint of the glass, 50 experiments were carried out to measure the time to initial crack and fallout. Temperatures were measured at the center of glass pane and edge, while the strain was measured at the edge. From the experimental data, the critical heat flux was determined under which no glass cracking takes place. By using the measured temperature and stress, the ultimate tensile stress of the glass edge was calculated. The obtained values were lower than the literature values for plain glass surface where no effect of micro defects at the cutting edge is taken into account. By analysing the post crack behavior, it was pointed out that the fallout area mainly depends on imposed heat flux and slightly on restraint. Under intense heating (more than 9kw/m2), large piece of glass tends to fall out, however under moderate heating, glass just cracks but did not fall out. Therefore it was pointed out that the application of the thermal stress model for glass breaking is limited to intensely heated scenarios. A simple prediction formula was derived for such scenarios.
Measurements of flame length, flame heat transfer and flame spread are made on onedimensional horizontal ceiling confined with two water-cooled soffits parallel to the flow field. Correlations with heat release rate are derived for flame length and flame heat transfer. Sensitivity to external heating and pilot flame intensity is studied on flame spread. Applicability of linearized flame spread theory for ceiling fires is examined using the test data.
The band profiles of ZnMgO/ZnO heterostructures were confirmed through surface potential measurements by Kelvin probe force microscopy. A simple model for the band profile was proposed and the various band parameters were evaluated experimentally and theoretically based on the band model. The band profile was calculated and validated with experimental results using the Schrödinger–Poisson equation. The energy level of the ZnMgO surface donor state, which serves as the source of the two-dimensional electron gas in ZnMgO/ZnO heterostructures, was estimated from the band parameters; nearly identical energy levels around 0.8 eV were obtained for Zn1−xMgxO layers with Mg compositions x ranging from 0.12 to 0.42 and the corresponding charge densities were estimated to be 8×1012 cm−2.
Ferroelectricity in stuffed aluminate sodalites, (Ca1−xSrx)8[AlO2]12(WO4)2 (x ≤ 0.2) (C1−xSxAW), is demonstrated in the present study. Pyroelectric measurements clarified switchable spontaneous polarization in polycrystalline C1−xSxAW, whose polarization values were on the order of 10 −2 C/cm 2 at room temperature. A weak anomaly in the dielectric permittivity at temperatures near the ferroelectric transition temperature suggested improper ferroelectricity of C1−xSxAW for all investigated values of x. A comprehensive study involving synchrotron X-ray powder diffraction measurements, molecular dynamics simulations, and first-principles calculations clarified that the ferroelectric phase transition of C1−xSxAW is driven by freezing of the fluctuations of WO4 tetrahedra in the voids of an [AlO2]12 12− framework. The voltage response and electromechanical coupling factor of C1−xSxAW estimated from the present results indicate that this material exhibits excellent performance as a pyroelectric energy harvester, suggesting that aluminate sodalites exhibit great promise as a class of materials for highly efficient energy harvesting devices.
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