Inter-channel crosstalk is one of the crucial issues in multichannel optical systems. Conventional studies assume that the crosstalk and the main signals have identical format. The present study, in contrast, considers different signal formats for the main and crosstalk lights, and shows that bit error degradation is different depending on the modulation format. Statistical properties of the crosstalk are also investigated. The result quantitatively confirms that a crosstalk light whose signal distribution is closer to a Gaussian profile causes larger degradation.

Question answering (QA) is the task of retrieving an answer in response to a question by analyzing documents. Although most of the efforts in developing QA systems are devoted to dealing with electronic text, we consider it is also necessary to develop systems for document images. In this paper, we propose a method of document image retrieval for such QA systems. Since the task is not to retrieve all relevant documents but to find the answer somewhere in documents, retrieval should be precision oriented. The main contribution of this paper is to propose a method of improving precision of document image retrieval by taking into account the co-occurrence of successive terms in a question. The indexing scheme is based on two-dimensional distributions of terms and the weight of co-occurrence is measured by calculating the density distributions of terms. The proposed method was tested by using 1253 pages of documents about the major league baseball with 20 questions and found that it is superior to the baseline method proposed by the authors.

Document retrieval is a fundamental but important task for intelligent access to a huge amount of information stored in documents. Although the history of its research is long, it is still a hard task especially in the case that lengthy documents are retrieved with very short queries (a few keywords). For the retrieval of long documents, methods called passage-based document retrieval have proven to be effective. In this paper, we experimentally show that a passage-based method based on window passages is also effective for dealing with short queries on condition that documents are not too short. We employ a method called "density distributions" as a method based on window passages, and compare it with three conventional methods: the simple vector space model, pseudo relevance feedback and latent semantic indexing. We also compare it with a passage-based method based on discourse passages.

Plating is applied to protect contact surfaces of contact devices such as switch, relay and connector from contaminations of oxidization and sulfuration etc. Furthermore it is known that the contact resistance can be reduced when there exist plated layers on the contact surfaces which have enough thickness and low resistivity compared with substratum materials. In this paper, contact resistance between plated conductors are calculated using three dimensional finite element method. Similariry, current density distribution in a contact spot with various resistivity of plated layers are shown and relative conductance depends on the contact area fraction with thickness of plated layers are presented.