RESUMO
We present a Time-to-Digital Converter (TDC) card with a compact form factor, suitable for multichannel timing instruments or for integration into more complex systems. The TDC Card provides 10 ps timing resolution over the whole measurement range, which is selectable from 160 ns up to 10 µs, reaching 21 ps rms precision, 1.25% LSB rms differential nonlinearity, up to 3 Mconversion/s with 400 mW power consumption. The I/O edge card connector provides timing data readout through either a parallel bus or a 100 MHz serial interface and further measurement information like input signal rate and valid conversion rate (typically useful for time-correlated single-photon counting application) through an independent serial link.
RESUMO
Classical molecular dynamics have been carried out in order to study the proton-transfer feasibility in immobilized imidazole arrays, taking into account their applications in new polymer electrolyte membrane fuel cells. The resulting trajectories have been analyzed with respect to the ability of forming hydrogen bonds, considering the angle distribution between the proton donor and acceptor groups. The dependence of the hydrogen-bond network is studied with respect to the variations of temperature, density of imidazole groups, and spacer lengths. According to the results, arrays of alkyl-imidazole molecules with three mobile CH(2) groups are the most favorable to a proton-transfer reaction. Regarding the alkyl-imidazole density, no significant difference for the arrays with a spacing of 6 or 7 A between the alkyl-imidazole molecules could be observed, whereas the 10 A array presents a lower probability of a proton transfer. The optimal arrangement of the investigated systems is a spacing of 6 A and a flexible chain length of three CH(2) groups. These results confirm previous experimental and simulation analyses.
