Katsuyuki Yamazaki

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The volume of mass unsolicited electronic mail, often known as spam, has recently increased enormously and has become a serious threat to not only the Internet but also to society. This paper proposes a new spam detection method which uses document space density information. Although it requires extensive e-mail traffic to acquire the necessary information,(More)
In this paper, we propose a new system for estimating walking paths, and people's indoor location (e.g., a floor or a room where user is staying) for life-logging. Our proposed system utilizes an acceleration sensor and an orientation sensor of an Android device, and the map matching with the preplotted vector map. Particularly emphasized new techniques in(More)
It is getting more difficult to monitor multiple services as well as to detect and/or to trace denial of service attacks with only tools showing graphs of the whole IP layer traffic like MRTG or by checking counters of router interfaces. In this paper, we discuss the specification of a software-based real-time measurement tool for flow which consists of(More)
It becomes so important to observe a wild life for obtaining not only knowledge of its biological behaviors but also interactions with human beings in terms of geoenvironmental investigation and assessment. A sensor network is considered to be a suitable and powerful tool to monitor and observe a wild life in fields. In order to monitor/observe seabirds, a(More)
The 6to4 method enables separate IPv6 sites to connect to the IPv6 Internet via a 6to4 relay router without an explicit IPv6-over-IPv4 tunnel setup. We have been operating a 6to4 relay router in Japan since March 2002, and started operating another relay router in the US from June 2003. This paper provides an analysis of IPv6 traffic through our 6to4 relay(More)
A network coordinate system (NCS) which predicts latencies between end-computers at low cost can achieve efficient resource selections on a large-scale distributed system such as a cloud computing. The NCS first decides coordinates of each computer on the pre-determined geometric space, and then estimates end-to-end latency by calculating a distance between(More)