Conventional retrieval methods of image database (IDB) systems are utilizing non-image information, or alphanumerical data, as keywords. These methods are suitable for document database systems, but not for IDB systems because the contents of image cannot be expressed by only such keywords. In this paper, a new image retrieval method using the layout structure" is proposed. This method can realize image retrieval based on the contents of image. Because, the layout structure means structural information such as object location and spatial relation and it corresponds to composition" of the image. This information, called region feature description (RED), is obtained in the input process of original images. In the retrieval process, we use some specified files which are created form RFD on the basis of each structural feature. Thus, interactive image retrieval based on structural information, that is composition", can be performed. Since India ink paintings are adopted as target images in this paper, it is difficult to extract and describe structural feature of object regions as they are. The structural information is described as geometrical feature by approximating them to simple polygons. As a result, composition" of the target image is obtained. This paper describes the description scheme and the extraction procedure of the structural information. And some experimental results are also presented to confirm the effectiveness of this method.

This paper reports on a theoretical study and modeling of a 1.55 µm quantum dot heterostructure laser using InN as a promising candidate for the first time. Details of design and theoretical analysis of probability distribution of the optical transition energy, threshold current density, modal gain, and differential quantum efficiency are presented considering a single layer of quantum dots. Dependence of threshold current density on the RMS value of quantum dot size fluctuations and the cavity length is studied. A low threshold current density of ∼51 Acm-2 is achieved at room temperature for a cavity length of 640 µm. An external differential efficiency of ∼65% and a modal gain of ∼12.5 cm-1 are obtained for the proposed structure. The results indicate that the InN based quantum dot laser is a promising one for the optical communication system.