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In this report, we explored the effect of incorporating ureidopyrimidone (UPy) linkers in a series of polyimides (Pis) previously studied in our laboratory. The polymers consist of an aromatic diamine monomer with a methylene linker, 4,4'-methylenebis (2,6-dimethylaniline), used to make a robust main chain along with aliphatic polyetherdiamine backbone linkers to decrease rigidity. The polymers were designed to exhibit thermal properties in between those of conventional aromatic PIs and polymers with wholly aliphatic ether diamine links, with an aim to improve the mechanical characteristics. Through dynamic mechanical analysis and differential scanning calorimetry, it is shown that the UPy linkers with their four-hydrogen bond sites are introduced to connect the chains in series. The connection strengthens the chain interactions and increases the range of the thermal and mechanical properties of the PI. Furthermore, the connecting regions are an important component to preserve the thermal stability of PIs while maintaining the processability. The polymers were characterized by FTIR, nuclear magnetic resonance, GPC, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, microhardness, and tensile testing., INTRODUCTION A series of thermoplastic polyimide with ureidopyrimidone linkers (PI-UPy) are synthesized and characterized in this work. The polymers are designed to have structural improvements and corresponding tractable properties. While [...]

With the need to reduce carbon emissions such as C[O.sub.2], hydrogen is being examined as potential 'clean' fuel for the future. One potential strategy is lean premixed combustion, where the fuel and air are allowed to mix upstream before entering the combustor, which has been proven to curb N[O.sub.x] formation in natural gas fired engines. However, premixing hydrogen and air may increase the risk of autoignition before the combustor, resulting in serious engine damage. A flow reactor was set up to test the ignition delay time of hydrogen and air at temperatures relevant to gas turbine engine operations to determine maximum possible mixing times. The results were then compared to past experimental work and current computer simulations. The current study observed that ignition is very sensitive to the initial conditions. The ignition delay times follow the same general trend as seen in previous flow reactor studies: ignition within hundreds of milliseconds and relatively low activation energy. An experimentally derived correlation by Peschke and Spadaccini (1985, 'Determination of Autoignition and Flame Speed Characteristics of Coal Gases Having Medium Heating Values,' Research Project No. 2357-1, Report No. AP-4291) appears to best predict the observed ignition delay times. Homogenous gas phase kinetics simulations do not appear to describe ignition well in these intermediate temperatures. Therefore, at the moment, only the current empirical correlations should be used in predicting ignition delay at engine conditions for use in the design of gas turbine premixers. Additionally, fairly large safety factors should still be considered for any design to reduce any chance of autoignition within the premixer. [DOI: 10.1115/1.2939007]

Experimental investigations were carried out to assess the use of hydrogen in a gasoline direct injection (GDI) engine. Injection of small amounts of hydrogen (up to 27% on energy basis) in the intake port creates a reactive homogeneous background for the direct injection of gasoline in the cylinder. In this way, it is possible to operate the engine with high exhaust gas recirculation (EGR) rates and, in certain conditions, to delay the ignition timing as compared to standard GDI operation, in order to reduce N[O.sub.x] and HC emissions to very low levels and possibly soot emissions. The results confirmed that high EGR rates can be achieved and N[O.sub.x] and HC emissions reduced, showed significant advantage in terms of combustion efficiency and gave unexpected results relative to the delaying of ignition, which only partly confirmed the expected behavior. A realistic application would make use of hydrogen-containing reformer gas produced on board the vehicle, but safety restrictions did not allow using carbon monoxide in the test facility. Thus, pure hydrogen was used for a best-case investigation. The expected difference in the use of the two gases is briefly discussed. [DOI: 10.1115/1.2795764]

Several numerical and analytical studies are conducted to explain the thermally driven combustion oscillatory behaviors of methane and hydrogen in a perfectly stirred reactor. These oscillations are shown to occur at the extinction turning point of the hysteresis curve.

A photoelectrochemical model is presented for hydrogen production from water electrolysis using proton exchange membrane. Results suggest an increase in hydrogen production with an increase in temperature.

The concept of the molecular formula to understand molecular composition and structure of fundamental compounds from 19th century, based on non-mathematical logic to modern technique is reviewed.