A novel time-frequency domain interference excision technique is proposed. The technique is based on adaptive biorthogonal local discrete cosine trans form (BLDCT). It uses a redundant library of biorthogonal local discrete cosine bases and an efficient concave cost function to match the transform basis to the interfering signal. The main advantage of the algorithm over conventional trans form domain excision algorithms is that the basis functions are not fixed but ca n be adapted to the time-frequency structure of the interfering signal. It is w e ll suited to transform domain compression and suppression of various types of in terference. Compared to the discrete wavelet transform (DWT) that provides logar ithmic division of the frequency bands, the adaptive BLDCT can provide more flex ible frequency resolution. Thus it is more insensitive to variations of jamming frequency. Simulation results demonstrate the improved bit error rate (BER) perf ormance and the increased robustness of the receiver.
Hydantoinase and N-carbamoylase play important rol es in the production of optically pure amino acids from racemic 5-monosubstitut ed hydantoins. In this report, hydantoinase and the N-carbamoylase from Burkh olderia cepecia.njut01 were purified to homogeneity by chromatography (Pharma cia Explorer 100 system). The substrate specificity, enantioselectivity, pH depe ndence of activity and temperature stability of the activity were characterized. The results show that the hydantoinase and N-carbamoylase induced from Burkh olderia cepecia.njut01 are both strict D-stereo selective enzymes. They both hydrolyze substrates with side chains containing aliphatic and aromatic res idues with higher activity and affinity toward aromatic than aliphatic substitu ted substrates. The hydantoinase is a homotetramer with subunit molecular weight near 52,000 and is active between pH 6.5 and 10 with an optimum near pH 9.0. The en zyme is active at temperatures up to 60°C, however,it appears instable at h ig her temperatures. The subunit molecular weight of N-carbamoylase is about 35KD. The N-carbamoylase is active in the pH range from 6.0 to 9.5. The optim-pH is 7.2 and the optimizing bioconversion temperature of the N-carbamyolase is 52 °C.
