Masaaki Tanizaki

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In this paper, we consider a traffic information sharing system based on Floating Car Data (FCD). FCD is one of the methods used to gather traffic information. It uses vehicles as sensor nodes that transmit their speed to the server. The server then broadcasts the updated speed data to all vehicles on the road so that vehicles can compute optimal travel(More)
Recommender systems support users in selecting items and services in an information-rich environment. Although recommender systems have been improved in terms of accuracy, such systems are still insufficient in terms of novelty and serendipity, giving unsatisfactory results to users. Two methods of “serendipitous recommendation” are therefore proposed.(More)
Telematics services, which provide traffic information such as route guidance, congestion warnings, etc. via a wireless communication network, have spread recently. The demand is growing for graphical guide information to be provided in addition to the conventional service that provides text only guidance. To improve graphical service, we propose a new(More)
In this paper, we present a <i>k</i>NN search method called the dual-heap <i>k</i>NN method, which is used in an embedded database management system (DBMS) for in-vehicle information systems. The dual-heap <i>k</i>NN method is based on two conventional <i>k</i>NN methods: (1) the RKV method and (2) the HS method. The RKV method and the HS method based on(More)
Map databases for car navigation systems loaded with hard disk drives are rewritable. Thus, the ability to update map databases in such systems is expected. Furthermore, because telematics services are available through cell phones with reasonable costs, it is also becoming possible to download new information into car navigation systems anywhere. Hence,(More)
Focusing on applying a spatial database management system to embedded devices, we present a spatial search processing method. First, we consider disk storage space to be a severe constraint in embedded devices, we propose a spatial index tree based on the PMR quadtree to reduce the required disk storage space. Second, since we consider it necessary to(More)