This paper describes a semi-fragile watermarking scheme for image authentication and tamper-proofing. Each watermark bit is duplicated and randomly embedded in the original image in the discrete wavelet domain by modifying the corresponding image coefficients through quantization. The modifications are made so that they have little effect on the image and that the watermarking is robust against tampering. The watermark image for authentication is reconstructed by taking a weighted vote on the extracted bits. The bits that lose the vote are treated as having been tampered with, and the locations of the lost bits as indicating tampered positions. Thus, authentication and tamper-proofing can be done by observing the images of watermarks that win and lose votes. Sieving, emphasis, and weighted vote were found to be effectively make the authentication and tamper detection more accurate. The proposed scheme is robust against JPEG compression or acceptable modifications, but sensitive to malicious attacks such as cutting and pasting.

Surface unconsolidated carbonates were sampled from lagoonal basins in the Shiraho and Sekisei Coral Reef areas, the Yaeyama Islands. Lime mud fractions were isolated from these carbonates by sieving and sedimentation methods to collect particles between 62.5 and 2 ,u. The isolated lime mud fractions were analyzed for carbonate-bound trace elements, C03 contents, mineralogical compositions by the X-ray diffraction analysis (XRD) , and petrographic observations including scanning electron microscope (SEM) observations. The carbonatebound trace element concentrations were determined by subtracting the 0.75 N LiCI-0.25 N CsCI in 60% ethanol leachable fraction from the 1 N ammonium acetate-acetic acid (pH adjusted to 5.2) leachable fraction. Lime mud is composed mineralogically by HMC (high-Mg calcite), HSA (high-Sr aragonite), LSA (low-Sr aragonite), and LMC (low-Mg calcite). However, the carbonate-bound Mg/Ca and Sr/Ca ratios are considerably lower in lime mud than the carbonate sand and gravels which contain the same amount of carbonate minerals with the lime mud. This suggests that Mg and Sr were leached without changing mineralogy during the formation of lime mud from coarse carbonate grains. Diagenetic changes in lime mud might have already started before its lithification processes to limestone.

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