Information and Media Technologies
Online ISSN : 1881-0896
ISSN-L : 1881-0896
3 巻 , 1 号
選択された号の論文の19件中1~19を表示しています
Hardware and Devices
Computing
  • Tatsuya Abe
    2008 年 3 巻 1 号 p. 13-25
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    Characterizing modal logic in first-order predicate logic is a hot research topic in mathematical logic. Van Benthem provided an elegant characterization in which the standard translation of modal formulas coincides with the class of first-order predicate formulas invariant for bisimulations. Whereas he characterized modal logic in first-order predicate logic at the level of formulas, we characterize modal logic in first-order predicate logic at the level of proofs. Specifically, we provide a complete translation from a term calculus based on intuitionistic modal logic into Barendregt's λP. This characterization, identified as the equality of proofs, is considered significant because a term calculus based on intuitionistic modal logic is expected to realize staged computation.
  • Kazuya Ogasawara, Satoshi Kobayashi
    2008 年 3 巻 1 号 p. 26-36
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    Tree Adjoining Grammar (TAG) is a useful grammatical tool to model RNA secondary structures containing pseudoknots, but its time complexity for parsing is not small enough for the practical use. Recently, Weinberg and Ruzzo proposed a method of approximating stochastic context free grammar by stochastic regular grammar and applied it to faster genome annotation of non-coding RNA families. This paper proposes a method for extending their idea to stochastic approximation of TAGs by regular grammars. We will also report some preliminary experimental results on how well we can filter out non candidate parts of genome sequences by using obtained approximate regular grammars.
  • Hiroshi Yamada, Kenji Kono
    2008 年 3 巻 1 号 p. 37-52
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    A recent trend in computing has been to leverage dormant PC resources. To achieve this, background applications such as peer-to-peer applications and PC Grid run on ordinary users' PCs, sharing their computing resources. If not properly managed, the background applications obtrude on the PC user's active jobs. In particular, the contention over disk bandwidth severely degrades performance. In this paper, we present DiscNice, a novel scheme for disk bandwidth management that can host background applications unobtrusively. Its novelty lies in the fact that it throttles disk I/O completely at the user-level. The user-level approach is attractive for heterogeneous environments such as differently configured PCs over the world; portability is enhanced and deployment is easier in comparison with kernel-level approaches. Experimental results suggest that our prototype DiscNice running on Linux 2.4.27 incurs 12% or less overhead, and gracefully ensures the unobtrusiveness of background applications.
Media (processing) and Interaction
  • Thi Thi Zin, Sung Shik Koh, Hiromitsu Hama
    2008 年 3 巻 1 号 p. 53-61
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    We propose a framework that enables vision-based navigation systems to more robustly recognize signboards. It is designed mainly for signboards with uniform color regions, which can be strongly affected by occlusion and reflection. The framework comprises two stages: preprocessing for extracting uniform color regions and recognizing them. In the first stage, the cumulative frequency, morphology gradient, and Mahalanobis distance are used for the extraction. In the second stage, a new matching method for identifying templates and a new relative method for verifying colors are used. Testing of a system using this framework and 300 images taken under various conditions showed a recognition rate of 98%, demonstrating the framework's powerful ability to recognize signboards.
  • Noritaka Osawa, Xiangshi Ren
    2008 年 3 巻 1 号 p. 62-70
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    Immersive virtual reality (VR) has long been considered an excellent environment in which to manipulate 3D virtual objects. However currently used immersive VR user interfaces have limitations. For example, while direct manipulation by hand is easy to understand and to use for approximate positioning, direct manipulation by hand is not suitable for making fine adjustments to virtual objects in an immersive environment because it is difficult to hold an unsupported hand in midair and then to release an object at a fixed point. We therefore propose a method that combines direct 3D manipulation by hand with a virtual 3D gearbox widget that we recently designed. Using this method, hand manipulation is used first to move virtual objects and place them in an approximate position, and then the widget is used to move them into a precise position. The experimental evaluation showed that this combination of direct manipulation by hand and the proposed gearbox is the best of five tested methods in terms of completion ratio of task and subjective preference.
  • Daisuke Tominaga, Fukumi Iguchi, Katsuhisa Horimoto, Yutaka Akiyama
    2008 年 3 巻 1 号 p. 71-78
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    In many cases of biological observations such as cell array, DNA micro-array or tissue microscopy, primary data are obtained as photographs. Specialized processing methods are needed for each kind of photographs because they have very wide variety, and often needed automated systems for modern high-throughput observations. We developed a fully-automated image processing system for cell array, high-throughput time series observation system for living cells, to evaluate gene expression levels and phenotype changes in time of each cell.
  • Jibin Yin, Xiangshi Ren
    2008 年 3 巻 1 号 p. 79-90
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    This paper investigates the interaction ability when introducing pressure into current basic interaction techniques by developing two novel techniques. A Zoom-based technique with pressure (hereafter referred to as ZWPS) is proposed to improve pixel-target selection. In this technique the pressure is used as a switch mode to couple a standard Point Cursor and a zoomable technique together. Pressure Scroll is also presented with a view to advancing scrolling performances by employing arc or line strokes to scroll documents. In this technique pressure is used as an additional control factor to widen the adjustable range of the scrolling velocity. We conducted two experiments to examine the effectiveness of ZWPS and Pressure Scroll. The experimental results indicate that they both bring significant benefits to the users.
  • Naomi Yamashita, Keiji Hirata, Toshihiro Takada, Yasunori Harada, Yosh ...
    2008 年 3 巻 1 号 p. 91-102
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    This paper outlines some of the benefits of providing remote users with consistent spatial referencing across sites when collaborating on physical tasks. Two video-mediated technologies are introduced: room-sized sharing that enables remote users to see similar things to what they would actually see if in the same room and a snapshot function that enables users to gesture at remote objects. We examine the impact of these technologies by comparing remote collaboration on physical tasks in a regular video conferencing system with a handy camera versus a room duplication system versus a room duplication system with a snapshot function. Results indicate that room-sized sharing facilitates remote collaborators' sense of co-presence and supports remote gesturing, which is closely aligned to normal co-present gesturing. Although such benefits did not contribute directly to the overall decrease of task performance, room-sized sharing and the snapshot function helped remote collaborators construct appropriate messages, efficiently establish joint focus, and monitor each others' comprehension when conducting complicated physical tasks.
  • Kevin J. Binkley, Masafumi Hagiwara
    2008 年 3 巻 1 号 p. 103-111
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    In particle swarm optimization (PSO) algorithms there is a delicate balance to maintain between exploitation (local search) and exploration (global search). When facing multimodal functions, the standard PSO algorithm often converges to a local minimum quickly, missing better opportunities. Methods such as non-global best neighborhoods increase exploration, but at the expense of slowing the convergence of the whole PSO algorithm. In this paper, we propose a new method to extend PSO, velocity-based reinitialization (VBR). VBR is both simple to implement and effective at enhancing many different PSO algorithms from the literature. In VBR-PSO, the velocities of the particles are monitored throughout the evolution, and when the median velocity of the swarm particles has dropped below a threshold, the whole swarm is reinitialized. Through VBR, the problem of premature convergence is alleviated; VBR-PSO focuses on one minimum at a time. In our experiments, we apply VBR to the global-best, local best, and von Neumann neighborhood PSO algorithms. Results are presented using the standard benchmark functions from the PSO literature. VBR enhanced PSO yields improved results on the multimodal benchmark functions for all PSO algorithms investigated in this study.
  • Tri Thanh Nguyen, Le Minh Nguyen, Akira Shimazu
    2008 年 3 巻 1 号 p. 112-130
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    Question classification, an important phase in question answering systems, is the task of identifying the type of a given question among a set of predefined types. This study uses unlabeled questions in combination with labeled questions for semi-supervised learning, to improve the precision of question classification task. For semi-supervised algorithm, we selected Tri-training because it is a simple but efficient co-training style algorithm. However, Tri-training is not well suitable for question data, so we give two proposals to modify Tri-training, to make it more suitable. In order to enable its three classifiers to have different initial hypotheses, Tri-training bootstrap-samples the originally labeled set to get different sets for training the three classifiers. The precisions of three classifiers are decreased because of the bootstrap-sampling. With the purpose to avoid this drawback by allowing each classifier to be initially trained on the originally labeled set while still ensuring the diversity of three classifiers, our first proposal is to use multiple algorithms for classifiers in Tri-training; the second proposal is to use multiple algorithms for classifiers in combination with multiple views, and our experiments show promising results.
Computer Networks and Broadcasting
  • Keiichi Shima, Koshiro Mitsuya, Tsuyoshi Momose, Shuichi Karino, Ryuji ...
    2008 年 3 巻 1 号 p. 131-147
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    Mobile IPv6 and NEMO BS are IETF standard mobility protocols for IPv6. It is said that freely available implementations play a big role in the deployment of new protocols. To accelerate the deployment of IPv6 mobility, we implemented the different mobility protocol stacks for the BSD operating systems. During the development, we made two different implementations based on this different design policies. The first one was an in-kernel implementation and the other a user space implementation. The former design makes it easy to use kernel information necessary for mobility operation, but it is difficult to implement and to extend features than the latter. The latter design needs to have extra mechanisms to retrieve or inject kernel information from user space, but in most cases developing user space programs is easier than developing in the kernel. In this paper, we discuss the design policies and implementation details of these two stacks.
  • Hirokazu Miura, Miki Yamamoto
    2008 年 3 巻 1 号 p. 148-155
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    Recently the content distribution networks (CDNs) have been highlighted as the new network paradigm which can improve latency for Web access. In CDNs, the content location strategy and request routing techniques are important technical issues. Both of them should be used in an integrated manner in general, but CDN performance applying both these technologies has not been evaluated in detail. In this paper, we investigate the effect of integration of these techniques. For request routing, we focus on a request routing technique applied active network technology, Active Anycast, which improves both network delay and server processing delay. For content distribution technology, we propose a new strategy, Popularity-Probability, whose aim corresponds with that of Active Anycast. Performance evaluation results show that integration of Active Anycast and Popularity-Probability can hold stable delay characteristics.
  • Takamasa Isohara, Keisuke Takemori, Iwao Sasase
    2008 年 3 巻 1 号 p. 156-164
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    Information protection schemes on mobile phones become important challenges because mobile phones have many types of private information. In general, user authentication and anomaly detection are effective to prevent attacks by illegal users. However, the user authentication can be applied only at the beginning of use and the conventional anomaly detection is not suited for mobile phones, only but computer systems. In this paper, we propose a simple and easy-to-use anomaly detection scheme on mobile phones. The scheme records the keystrokes as the mobile phone is operated, and an anomaly detection algorithm calculates a score of similarity, to detect illegal users. We implemented a prototype system on the BREW (Binary Run-time Environment for Wireless) emulator and evaluated error rates by using results from 15 testers. From experiments results, we show the proposed scheme is able to apply the anomaly detection by checking the similarity score several times.
  • Hisashi Mohri, Ikuya Yasuda, Yoshiaki Takata, Hiroyuki Seki
    2008 年 3 巻 1 号 p. 165-177
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    In an ad hoc network, we cannot assume a trusted certificate authority and a centralized repository that are used in ordinary Public-Key Infrastructure (PKI). Hence a PKI system of the web-of-trust type in which each node can issue certificates to others in a self-organizing manner has been studied. Although this system is useful for ad hoc networks, it has the problem that for authentication a node needs to find a certificate-chain to the destination node. In this paper, we formally model a web-of-trust-type PKI system, define the certificate-chain discovery problem, and propose a new distributed algorithm and its modification that solve the problem. Furthermore, we propose a measure of communication cost, and according to the measure, we compare our algorithm with an existing method by numerical computation for large-size networks and by simulation on randomly generated unit disk graphs for moderate-size networks. The simulation results show that the communication cost of the proposed method is less than 10% of the existing method.
  • Niwat Thepvilojanapong, Shinji Motegi, Hiroki Horiuchi
    2008 年 3 巻 1 号 p. 178-190
    発行日: 2008/03/15
    公開日: 2008/03/15
    ジャーナル フリー
    Collision Warning Systems (CWS) can help reduce the probability and severity of car accidents by providing some sort of appropriate warning to the driver through Inter-Vehicle Communication (IVC). Especially, the CWS can help avoid collision at intersections where traffic accidents are frequent (Study Group for Promotion of ASV; Traffic Bureau, 2007). A vehicle equipped with the CWS periodically broadcasts its information, and the CWS on other vehicles use the received information to alert drivers, helping them become aware of the existence of other vehicles. To avoid collision, the CWS has concrete objectives of IVC, i.e., the CWS should receive useful information accurately and in time. Many IVC protocols including our previously proposed relay control protocol (Motegi, et al., 2006) have been developed and evaluated through traditional metrics. However, instead of using such traditional metrics directly, many requirements of the intersection CWS must be considered to judge the feasibility and practicability of IVC protocols. This paper shows performance evaluation of our previous IVC protocol developed for CWS. To study the behavior of IVC protocols, we first describe a simulation methodology including performance metrics by means of reliable and timely communications. We then use such metrics to compare our IVC protocol with the flooding protocol in large-scale simulated networks. The simulation results show that our previously proposed protocol is a good candidate for real implementation because it passes all requirements of the intersection CWS.
Information Systems and Applications
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