Chiba, Japan

Tokyo University of Information science is a private university in Wakaba Ward of the city of Chiba, Chiba Prefecture, Japan. The university was established in 1988 by the School corporation Tokyo University of Agriculture. The university consists of four departments: Information System, Environmental Information, Business & Information, and Media & Cultural Studies. To follow the rapid period changing and better contribution for our society, we always make our best on student education of their creativity and excellent personality. Wikipedia.

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Gozolchiani A.,Bar - Ilan University | Havlin S.,Bar - Ilan University | Yamasaki K.,Tokyo University of Information Sciences
Physical Review Letters | Year: 2011

We construct and analyze a climate network which represents the interdependent structure of the climate in different geographical zones and find that the network responds in a unique way to El Niño events. Analyzing the dynamics of the climate network shows that when El Niño events begin, the El Niño basin partially loses its influence on its surroundings. After typically three months, this influence is restored while the basin loses almost all dependence on its surroundings and becomes autonomous. The formation of an autonomous basin is the missing link to understand the seemingly contradicting phenomena of the afore-noticed weakening of the interdependencies in the climate network during El Niño and the known impact of the anomalies inside the El Niño basin on the global climate system. © 2011 American Physical Society.

Nishimura A.,Tokyo University of Information Sciences
Proceedings - 7th International Conference on Intelligent Information Hiding and Multimedia Signal Processing, IIHMSP 2011 | Year: 2011

Reversible data hiding is a technique where hidden data is embedded in host data, such that the consistency of the host is perfectly preserved and the host data is restored during the extraction process of the hidden data. Herein, improvements to the conventional technique for reversible data hiding of audio waveforms are proposed. As no location map is required to prevent amplitude overflow, the proposed method achieves a storage capacity of nearly 1 bit per sample of payload data. The proposed method is superior in terms of having a smaller loss of payload data and little objective quality degradation on average. Concealment of payload within the host data is also better than when using the conventional method. © 2011 IEEE.

Yoon M.-G.,Gangneung - Wonju National University | Tsumura K.,Tokyo University of Information Sciences
Automatica | Year: 2011

This paper presents explicit forms of transfer functions for a class of cyclic consensus systems with different kinds of network topologies; directed, undirected and different numbers of reference agents. Each agent of consensus systems is assumed to satisfy a scalar integrator dynamics which is driven by a common consensus protocol and an independent exogenous input. It is shown that every single-input single-output (SISO) transfer function between the exogenous input of one agent and the state of another generally different agent, is always minimum phase. In addition, the poles and zeros, system degrees and relative degrees of those SISO transfer functions are specified. These results are interpreted in relation to the controllability and closed loop performance of a networked system with one leader agent. Furthermore, our transfer function representations are applied to an investigation of stability margins for a closed loop cyclic consensus system. © 2011 Elsevier Ltd. All rights reserved.

Iwata Y.,Tokyo University of Information Sciences
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

Measure and Conquer is a recently developed technique to analyze worst-case complexity of backtracking algorithms. The traditional measure and conquer analysis concentrates on one branching at once by using only small number of variables. In this paper, we extend the measure and conquer analysis and introduce a new analyzing technique named "potential method" to deal with consecutive branchings together. In potential method, the optimization problem becomes sparse; therefore, we can use large number of variables. We applied this technique to the minimum dominating set problem and obtained the current fastest algorithm that runs in O(1.4864 n ) time and polynomial space. We also combined this algorithm with a precalculation by dynamic programming and obtained O(1.4689 n ) time and space algorithm. These results show the power of the potential method and possibilities of future applications to other problems. © 2012 Springer-Verlag.

Nishimura A.,Tokyo University of Information Sciences
International Journal of Innovative Computing, Information and Control | Year: 2010

A technique for audio data hiding by using subband amplitude modulation was evaluated by computer simulations in terms of robustness with respect to the cumulative effects of reverberations, background noise, and encoding and decoding with a speech codec. Speech signals from 22 speakers and signals from 100 pieces of music were used as the host audio data. Computer simulations revealed that speech and music signals with background noise and reverberations were able to transmit at least 80% of the embedded data at 8 bps after encoding and decoding using the Adaptive Multi-Rate (AMR) speech codec at a bitrate of 12.2 kbps. In actual measurements in a reverberant room using a cell phone terminal, data hidden in a 12.2-kbps AMR recording having a signal-to-noise ratio of 20 dB was detected at a mean bit error rate of 15 %. The sound quality degradation induced by data hiding was objectively measured using the perceptual evaluation of speech quality (PESQ) and perceptual evaluation of audio quality (PEAQ) algorithms. The average PESQ score of the speech signals approximately corresponded to a subjective evaluation of 'fair', while the average PEAQ score of the music signals corresponded to a somewhat lower subjective evaluation of 'slightly annoying'. ©2010 ISSN 1349-4198.

Kobayashi N.,Tokyo University of Information Sciences
Journal of the ACM | Year: 2013

We propose a novel verification method for higher-order functional programs based on higher-order model checking, or more precisely, model checking of higher-order recursion schemes (recursion schemes, for short). The most distinguishing feature of our verification method for higher-order programs is that it is sound, complete, and automatic for the simply typed λ-calculus with recursion and finite base types, and for various program verification problems such as reachability, flow analysis, and resource usage verification. We first show that a variety of program verification problems can be reduced to model checking problems for recursion schemes, by transforming a program into a recursion scheme that generates a tree representing all the interesting possible event sequences of the program. We then develop a new type-based model-checking algorithm for recursion schemes and implement a prototype recursion scheme model checker. To our knowledge, this is the first implementation of a recursion scheme model checker. Experiments show that ourmodel checker is reasonably fast, despite the worst-case time complexity of recursion scheme model checking being hyperexponential in general. Altogether, the results provide a new, promising approach to verification of higher-order functional programs. © ACM 2013.

Gall F.L.,Tokyo University of Information Sciences
Proceedings - Annual IEEE Symposium on Foundations of Computer Science, FOCS | Year: 2014

In this paper we present a quantum algorithm solving the triangle finding problem in unweighted graphs with query complexity Õ(n5/4)) where n denotes the number of vertices in the graph. This improves the previous upper bound O(n9/7) = O(n1.285) recently obtained by Lee, Magniez and Santha. Our result shows, for the first time, that in the quantum query complexity setting unweighted triangle finding is easier than its edge-weighted version, since for finding an edge-weighted triangle Belovs and Rosmanis proved that any quantum algorithm requires O(n9/7 vlog n) queries. Our result also illustrates some limitations of the non-adaptive learning graph approach used to obtain the previous O(n9/7) upper bound since, even over unweighted graphs, any quantum algorithm for triangle finding obtained using this approach requires v(n9/7 log n) queries as well. To bypass the obstacles characterized by these lower bounds, our quantum algorithm uses combinatorial ideas exploiting the graph-theoretic properties of triangle finding, which cannot be used when considering edge-weighted graphs or the non-adaptive learning graph approach. © 2014 IEEE.

Hirai H.,Tokyo University of Information Sciences
Mathematical Programming | Year: 2013

In this paper, we establish a novel duality relationship between node-capacitated multiflows and tree-shaped facility locations. We prove that the maximum value of a tree-distance-weighted maximum node-capacitated multiflow problem is equal to the minimum value of the problem of locating subtrees in a tree, and the maximum is attained by a half-integral multiflow. Utilizing this duality, we show that a half-integral optimal multiflow and an optimal location can be found in strongly polynomial time. These extend previously known results in the maximum free multiflow problems. We also show that the set of tree-distance weights is the only class having bounded fractionality in maximum node-capacitated multiflow problems. © 2011 Springer and Mathematical Optimization Society.

Nishimura A.,Tokyo University of Information Sciences
Proceedings of Meetings on Acoustics | Year: 2013

Various attacks on robust audio watermarking have been proposed. Excessive intentional modifications and/or perceptual coding to the distributed stego audio degrades sound quality and can prevent the extraction of hidden data so that piracy detection systems using automated watermarking and crawling are disrupted. Reversible signal processing attacks, such as linear speed changes, also degrade the sound quality of distributed stego audio. However, the inverse processing of the reversible processing attack can recover the original sound quality of the audio received after illegal distribution. Therefore, the degradation of sound quality induced by perceptual codecs and reversible processing attacks followed by inverse processing should be considered to determine whether the intensity of these attacks is realistic. In this study, objective audio quality measurement was applied to audio signals, including typical perceptual coding, MP3, tandem MP3, and MPEG4AAC, and reversible signal processing techniques, including linear speed change, noise addition, frequency scale modification, time scale modification, bandpass filtering and echo addition. The results provide requirements that watermarking should be robust against and a list of attacks that are feasible against high-quality audio watermarking. © 2013 Acoustical Society of America.

Le Gall F.,Tokyo University of Information Sciences
Proceedings of the Annual ACM-SIAM Symposium on Discrete Algorithms | Year: 2012

We present new quantum algorithms for Boolean Matrix Multiplication in both the time complexity and the query complexity settings. As far as time complexity is concerned, our results show that the product of two n x n Boolean matrices can be computed on a quantum computer in time Õ(n 3/2 + nℓ 3/4), where ℓ is the number of non-zero entries in the product, improving over the output-sensitive quantum algorithm by Buhrman and Spalek that runs in Õ(n 3/2√ℓ) time. This is done by constructing a quantum version of a recent algorithm by Lingas, using quantum techniques such as quantum counting to exploit the sparsity of the output matrix. As far as query complexity is concerned, our results improve over the quantum algorithm by Vassilevska Williams and Williams based on a reduction to the triangle finding problem. One of the main contributions leading to this improvement is the construction of a triangle finding quantum algorithm tailored especially for the tripartite graphs appearing in the reduction. Copyright © SIAM.

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