Naonobu Okazaki

On a serendipity-oriented recommender system based on folksonomy

This paper proposes a recommendation method that focuses on not only predictive accuracy but also serendipity. On many of the conventional recommendation methods, items are categorized according to their attributes (a genre, an authors, etc.) by the recommender in advance, and recommendation is made using the results of the categorization. In this study, impressions of users to items are adopted as a feature of the items, and each item is categorized according to the feature. Impressions used in such categorization are prepared using folksonomy, which classifies items using tags given by users. Next, the idea of “concepts” was introduced to avoid synonym and polysemy problems of tags. “Concepts” are impressions of users on items inferred from attached tags of folksonomy. The inferring method was also devised. A recommender system based on the method was developed in java language, and the effectiveness of the proposed method was verified through recommender experiments.

Proposal of a Robust Zone-based Hierarchical Routing Method for Ad Hoc Networks

Ad hoc routing protocols can be divided into two categories. One is proactive schemes, the other is reactive schemes. Two schemes have advantage and disadvantage each other. There are hybrid schemes which are good mix of proactive schemes and reactive schemes. In hybrid schemes, nodes maintain the complete routing information of particular area only. Outside of this area, a node search for a route only when it needs to forward a packet. In consequence, the communication overhead is reduced zone-based hierarchical link state (ZHLS) routing protocol is proposed as a hybrid scheme. However, ZHLS take time to search new route when route is disconnected because it search only one route. In particular, real-time application is severely-impacted by this delay. For this reason, it is necessary to construct multiple routes as backup route. In this paper, we propose multiple-route zone-based hierarchical source routing (called MR-ZHSR) scheme that extends ZHLS routing protocol to construct multi-path routes

An Authentication Method Independent of Tap Operation on the Touchscreen of a Mobile Device

At the present time, mobile devices such as tablet-type PCs and smart phones have widely penetrated into our daily lives. Therefore, an authentication method that prevents shoulder surfing is needed. We are investigating a new user authentication method for mobile devices that uses surface electromyogram (s-EMG) signals, not screen touching. The s-EMG signals, which are generated by the electrical activity of muscle fibers during contraction, are detected over the skin surface. Muscle movement can be differentiated by analyzing the s-EMG. In this paper, a series of experiments was carried out to investigate the prospect of an authentication method using s-EMGs. Specifically, several gestures of the wrist were introduced, and the s-EMGs generated for each motion pattern were measured. We compared the s-EMG patterns generated by each subject with the patterns generated by other subjects. As a result, it was found that each subject has similar patterns that are different from those of other subjects. Thus, sEMGs can be used to confirm one’s identification for authenticating passwords on touchscreen devices.

On a Serendipity-oriented Recommender System based on Folksonomy and its Evaluation☆

Abstract The present paper proposes a recommendation method that focuses not only on predictive accuracy but also serendipity. In many of the conventional recommendation methods, items are categorized according to their attributes (genre, author, etc.) by the recommender in advance, and recommendations are made using the categorization. In the present study, the impression of users regarding an item is adopted as its feature, and items are categorized according to this feature. Such impressions are derived using folksonomy. A recommender system based on the proposed method was developed in the Java language, and the effectiveness of the proposed method was verified through recommender experiments.

Proposal for a practical cipher communication protocol that can coexist with NAT and firewalls

Threats to network security have become a serious problem, and encryption technologies for communications are an important issue these days Although the security of IPsec ESP (, that is a typical existing cipher communication technology) is strong, it has such problems that it can not be used in the environment where it coexists with NAT and firewalls, and that there also exists some degradation of throughput For such reasons, ESP is used only for some limited applications such as VPN (Virtual Private Network) In this paper, we propose a new cipher communication protocol, called PCCOM (Practical Cipher COMmunication), that can verify the identity of the corresponding counterpart and assure the integrity of packets in the environment where it coexists with NAT and firewalls, without changing the format of the original packets To confirm the effectiveness of PCCOM, we installed a trial system in FreeBSD, and confirmed the coexistibility with NAT and firewalls We also measured its throughput, and good performance was confirmed, which is attributable to “no change” of the packet format.

A new test sequence generation method for interoperability testing

A method for generating test sequences for interoperability testing of communication systems is proposed. In the proposed method, the system state graph, which shows behaviours of the whole system, is generated from protocol specifications, and test sequences that confirm each transition and the state based on this graph are generated. The method is characterized in that the states of individual processes are confirmed, considering independency of the two processes, which is a characteristic of the interoperability testing. An application for a simple protocol with a retransmission mechanism shows that we can improve testing reliability in interoperability testing. Using this method is expected to decrease cost for generating test sequences.

Novel Unsupervised SPITters Detection Scheme by Automatically Solving Unbalanced Situation

Spam over Internet telephony (SPIT) is recognized as a new threat for voice communication services such as voice over Internet protocol (VoIP). Due to the privacy reason, it is desired to detect SPITters (SPIT callers) in a VoIP service without training data. Although a clustering-based unsupervised SPITters detection scheme has been proposed, it does not work well when the SPITters account for a small fraction of the entire caller. In this paper, we propose an unsupervised SPITters detection scheme by adding artificial SPITters data to solve the unbalanced situation. The key contribution is to propose a novel way to automatically decide how much artificial data should be added. We show that classification performance is improved by means of computer simulation with real and artificial call log data sets.

Evaluation of feature values of surface electromyograms for user authentication on mobile devices

At the present time, mobile devices, such as tablet-type PCs and smart phones, have widely penetrated into our daily lives. Therefore, an authentication method that prevents shoulder surfing is needed. We are investigating a new user authentication method for mobile devices that use surface electromyogram (s-EMG) signals, not screen touching. The s-EMG signals, which are generated by the electrical activity of muscle fibers during contraction, are detected over the skin surface. Muscle movement can be differentiated by analyzing the s-EMG. In this paper, a method that uses a list of gestures as a password is proposed. And also, results of experiments are presented that was carried out to investigate the performance of the method extracting feature values from s-EMG signals (using the Fourier transform) adopted in this research.

A New User Authentication Protocol for Mobile Terminals in Wireless Network

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