Raphael Garcia Moreira

R.G. Moreira, L.H. Higa Moreira and S.G. dos Santos Filho
This work proposes a new geometry for an Ion Mobility Spectrometer (IMS) in order to detect toluene, 2-propanol and water vapor. The IMS system was designed with a compact ionization chamber followed by another capable of selectively discriminate the range radius of the charged ions that collides to lateral sensing electrodes under a bidimensional distribution of high electric fields (0.0 to 27kV/cm) and under a stationary flow regime of ions, without turbulence, using a vacuum pump coupled to the chamber. The MATLAB platform was employed to solve the equations that describes the ion trajectories as a function of their mass and the Quickfield6.3 program was employed to simulate the bidimensional distribution of high electric fields under a stationary flow regime of ions without turbulence. The results showed a good fit of the range radius of the ionized species with the position of the lateral sensing electrodes after measuring the current intensity associated to the different ionic masses obtained from the ionization of toluene, 2-propanol and water, respectively.

R.G. Moreira; L.H. Higa Moreira; S.G. dos Santos Filho
This work proposes a set up for sensing H 2 , CH 4 and CO generated from biomass. The sensing is performed by commercially avaliable SnO 2 chemiresistors [6], one for each gas. The proposed set up has a gas dilution stage before the sensing step. One hundred and twenty five different gas mixtures were prepared from the combination of H 2 , CH 4 and CO using nitrogen as carrier gas. The samples were evaluated under two different methods for sensor recovery: forced and natural. Based on the results, it was established that the cross sensitivities of the CO and CH 4 sensors are too high while the H 2 sensor presents selectivity of almost 100%. Also, the natural recovery method showed improved results because of the better thermal stability of the system. An artificial neural network was developed with the purpose of overcoming the problem of cross-sensitivities and indicated a minimum squared error energy (SSE) of 8.5×10 -8 for H 2 , 2.0×10 -3 for CH 4 and 5.1×10 -3 for CO.