Dicalcium phosphate dihydrate (DCPD, CaHPO 4 •2H 2 O), also known as brushite, is one of the important bioceramics due to not only diseases factors such as kidney stone and plaque formation but also purpose as fluoride insolubilization material. It is used medicinally to supply calcium, and is of interest for its unique properties in biological and pathological mineralization. It is important to control the crystal morphology of brushite since its chemical reactivity depends strongly on its surface properties; thus, its morphology is a key issue for its applications as a functional material or precursor for other bioceramics. Here, we report the effects of the initial pH and the Ca and phosphate ion concentrations on the morphology of DCPD particles during aqueous solution synthesis. Crystal morphologies were analyzed by scanning electron microscopy and X-ray diffraction. The morphology phase diagram of DCPD crystallization revealed that increasing the initial pH and/or ion concentration transformed DCPD morphology from petal-like into plate-like structures.

DCPD, dicalcium phosphate dihydrate (CaHPO 4 •2H 2 O) reacts with fluoride ion in an aqueous solution, and forms fluorapatite (FAp, Ca 10 (PO 4 )6F 2 ). In previous study, we have found that DCPD does not react with fluoride ion directly, but show few hours of induction period by reaction with fluoride. In this study, effect of hydroxyapatite (HA, Ca 10 (PO 4 ) 6 (OH) 2 ) on the reactivity of DCPD with fluoride ion was investigated. By mixing HA with DCPD, it was appeared that the induction period of the reaction was shortened. Morphology of the obtained FAp was similar to HA paricles. We carried on coating of HA on the DCPD particle by soaking DCPD in simulated body fluid (SBF, Kokubo Solution). By coating HA on DCPD particles, particle morphology of the obtained FAp was consistency to the DCPD particles. These results suggest that the shape and particle size of FAp after reaction of DCPD is controllable by DCPD particle as template, and coating with HA. Effect of Hydroxyapatite on

Dicalcium phosphate dihydrate (DCPD) reacts with fluoride ion in an aqueous solution and forms stable fluoroapatite (FAp). This reaction requires a lag time to form nano-sized precursor, hydroxyapatite (HAp)-like calcium phosphate, on DCPD surface. This long lag time prevents DCPD from applying as an effective fluoride removal agent from waste water. The purpose of this study is to improve the reactivity of DCPD with fluoride ion by HAp-coating on the DCPD surface by soaking it in the simulated body fluid (SBF) under various DCPD/SBF ratios and soaking periods. The results showed the HAp-coating on DCPD by soaking in the SBF reduced the lag time to be negligible with increasing in amount of HAp up to 2 % in mass to the DCPD; however, further HAp formation had no affects on improvement of the reactivity.

SUMMARYThis paper describes a blind watermarking scheme through cyclic signal processing. Due to various rapid networks, there is a growing demand of copyright protection for multimedia data. As efficient watermarking of images, there exist two major approaches: a quantizationbased method and a correlation-based method. In this paper, we proposes a correlation-based watermarking technique of three-dimensional (3-D) polygonal models using the fast Fourier transforms (FFTs). For generating a watermark with desirable properties, similar to a pseudonoise signal, an impulse signal on a two-dimensional (2-D) space is spread through the FFT, the multiplication of a complex sinusoid signal, and the inverse FFT. This watermark, i.e., spread impulse signal, in a transform domain is converted to a spatial domain by an inverse wavelet transform, and embedded into 3-D data aligned by the principle component analysis (PCA). In the detection procedure, after realigning the watermarked mesh model through the PCA, we map the 3-D data on the 2-D space via block segmentation and averaging operation. The 2-D data are processed by the inverse system, i.e., the FFT, the division of the complex sinusoid signal, and the inverse FFT. From the resulting 2-D signal, we detect the position of the maximum value as a signature. For 3-D bunny models, detection rates and information capacity are shown to evaluate the performance of the proposed method.

No abstract