Transient failure analysis of liquid-filled shells Part I: Theory

In this paper, the governing equations which consider dynamic fluid-structure interaction, modal coupling in both axial and circumferential directions, and dynamic buckling are derived. The various pressure components acting on the shell wall due to a seismic event are also analyzed. The matrix equation of motion for liquid-filled shells is obtained through a Galerkin/Finite Element discretization procedure. The modal coupling among the various combinations of axial and circumferential modes are identified with a particular reference to the fluid-structure system under seismic excitation. Finally, the equations for the dynamic stability analysis of liquid-filled shells are presented.     

Subsensitivity to bronchoprotection against adenosine monophosphate challenge following regular once-daily formoterol

Questions about usual drinking play an important role in the construction of alcohol consumption measures. However, little is known about difficulties in answering these questions for respondents with variability in their drinking patterns. We investigated this in a community sample of 945 drinkers and in a clinical sample of 400 patients treated for alcohol and/or drug problems. Demographic variables were not consistently related to self-reported difficulty in answering, but a diagnosis of current DSM-IV alcohol dependence was significantly related in both samples. In modeling the relationship between alcohol consumption and DSM-IV alcohol dependence, the fit of the model to the data was significantly improved by the addition of a variable indicating respondents' difficulty answering the usual drinking questions. Using this information in the development of alcohol consumption questions may provide more precise estimates of the risk from alcohol consumption to outcomes such as alcohol dependence.     

Reliability and degradation of small molecule-based organiclight-emitting devices (OLEDs)

Studies of degradation mechanisms in small molecule-based organic light-emitting devices (OLEDs) are reviewed. A special emphasis is given to OLEDs based on tris (8-hydroxyquinoline) aluminum (AlQ₃), an emitter and electron transport material used in the majority of OLEDs emitting from the green to the red part of the spectrum. Different strategies used for increasing device stability are addressed and the models proposed to explain experimental observations related to OLED operational stability are discussed. Although none of the presently proposed models can explain all experimental observations, the largest body of experimental evidence appears to be consistent with a model based on the instability of cationic AlQ₃ species, produced by the injection of holes into the AlQ₃ electron transport and emitter layer. Other models may be of importance in explaining degradation behavior on different time scales. Models based on redistribution of space charge appear to be responsible for reversible short-term degradation, while a model based on indium migration may be important for degradation on very long time scales     

Parametric study of instantaneous heat transfer based on multidimensional model in direct-injection hydrogen-fueled engine

This paper presents a parametric study on instantaneous heat transfer of a direct-injection hydrogen-fueled engine using a multidimensional model. A simplified single-step mechanism was considered for estimating the reaction rate of hydrogen oxidation. The modified wall-function was used for resolving the near-wall transport. An arbitrary Lagrangian–Eulerian algorithm was adopted for solving the governing equations. Experimental measurements were implemented to verify the developed model. They show that the instantaneous heat-transfer model is sufficiently accurate. The influence of engine speed, equivalence ratio, and the start of injection timing were investigated. The flow fields appeared to have greater size vectors and coarser distribution with an increase of engine speed. A heterogeneous distribution was obtained for an ultra-lean mixture condition (φ ≤ 0.5), which decreased with an increase of equivalence ratio. There was no pronounced influence of the start of injection on the flow field pattern and mixture homogeneity. Thermal field analysis was used to demonstrate trends in the instantaneous heat transfer. It was observed that there was a crucial distinction between the lean and ultra-lean mixtures as well as the engine speed. Furthermore, a non-uniform behavior was found for the impact of the equivalence ratio on temperature distribution. It is clear that the developed models are powerful tools for estimating the heat transfer of the hydrogen-fueled engine. The developed predictive correlation is highly accurate in predicting the heat transfer of the hydrogen-fueled engine, focusing on the equivalence ratio as a governing variable.     

Preparation and Characterization of Biodegradable Polyurethane Nanocomposites Based on Poly(3-hydroxybutyrate) and Poly(Butylene Adipate) Using Reactive Organoclay

Polyurethane nanocomposites were synthesized using one-step solution polymerization of poly(3-hydroxybutyrate)-diol, poly(butylene adipate)-diol using 1,6-hexamethylene diisocyanate. Nanocomposites were prepared using an in-situ polymerization method. The structure was verified using FTIR and ¹HNMR. Morphology was examined by XRD and TEM methods. Thermal properties were examined using DSC and TG. DSC showed that all samples were semicrystalline. The Cloisite 30B enhanced the melt crystallization of PHB segments while hindering those of the PBA segments. Thermal stability was improved compared to the neat PUs samples. The Coats-Redfern model was used to calculate the activation energy. Mechanical properties were improved with incorporation of organoclays.     

Influence of flexible substrates on inverted organic solar cells using sputtered ZnO as cathode interfacial layer

Zinc oxide (ZnO) has recently shown to be of considerable interest for the development of interfacial buffer layers in inverted organic solar cells (OSCs). High quality ZnO thin films can indeed be prepared on large-area ITO-coated flexible substrates, using low temperature deposition techniques such as sputtering, a compatible technique with roll-to-roll process. However, further studies are still needed for a better understanding of the influence of the flexible substrate properties on the photovoltaic performances of those devices. In this work, ZnO films have been sputtered on ITO-coated flexible (PEN) substrates and annealed at different temperatures. The role of the surface morphology and the crystalline quality of ZnO films has been investigated. In the window of flexible compatible process, we found that moderate annealing temperatures of ZnO (?180 °C) lead to improved structural properties and performances. Interestingly, we achieve optimal performances for an annealing temperature of 160 °C, resulting in power conversion efficiency (PCE) equivalent to the highest performances usually achieved on rigid cells.     

Thermal and mechanical properties of injection moulded heat-treated oil palm empty fruit bunch fibre-reinforced high-density polyethylene composites

ABSTRACT

Oil palm empty fruit bunch (OPEFB) was heat treated at 180°C using a vacuum oven for one hour, extruded and compounded with high-density polyethylene at 10%, 20% and 30% weight fraction. The composites then were injection moulded into dumb-bell shaped specimens. The effect of composition and heat treatment on the thermal properties of composites were investigated using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The tensile and flexural properties were also tested using an Instron Universal Testing Machine. TGA shows an increase in the degradation peak temperature of the heat-treated composites. DSC revealed an increasing trend in the degree of crystallinity (X_c) of the matrix as the heat-treated empty fruit bunch was used as a filler. An increment in the tensile modulus and tensile strain were observed for the treated fibre composites. In addition, the tensile strength value was increased for treated fibre composites with lower fibre loading.