Multiresolution,perceptual and vector quantization based video codec

This paper presents a novel Multiresolution, Perceptual and Vector Quantization (MPVQ) based video coding scheme. In the intra-frame mode of operation, a wavelet transform is applied to the input frame and decorrelates it into its frequency subbands. The coefficients in each detail subband are pixel quantized using a uniform quantization factor divided by the perceptual weighting factor of that subband. The quantized coefficients are finally coded using a quadtree-coding algorithm. Perceptual weights are specifically calculated for the centre of each detail subband. In the inter-frame mode of operation, a Displaced Frame Difference (DFD) is first generated using an overlapped block motion estimation/compensation technique. A wavelet transform is then applied on the DFD and converts it into its frequency subbands. The detail subbands are finally vector quantized using an Adaptive Vector Quantization (AVQ) scheme. To evaluate the performance of the proposed codec, the proposed codec and the adaptive subband vector quantization coding scheme (ASVQ), which has been shown to outperform H.263 at all bitrates, were applied to six test sequences. Experimental results indicate that the proposed codec outperforms the ASVQ subjectively and objectively at all bit rates.     

Stability and Degradation Processes of 2,4,6-Trinitrotoluene (TNT) on Metal Oxide Surfaces

The chemical stability of 2,4,6-trinitrotoluene (TNT) when placed in physical contact with metal oxide surfaces is investigated. The TNT is deposited at 1–3 monolayers of coverage on the surface of microcrystalline MnO₂, CuO, WO₃, MoO₃, Bi₂O₃, SnO₂, and Fe₂O₃ by wet impregnation. The samples were placed in a 50°C oven and allowed to react over a period of 11 months. Periodically, samples were removed and analyzed chromatographically to determine whether products were being formed at the surface of the oxide. TNT proved to be inert to most oxides; however, both CuO and MnO₂ effected a clean decomposition of the TNT into tri-nitrobenzene.