Foundation of Computer Science Laboratory

Takafumi Hayashi Associate Professor	Shuxue Ding Assistant Professor

The research and education activities in the laboratory focus on the theoretical foundations of computers and computations, including broad applications in science and engineering. Our work covers algorithms and computation, programming languages, discrete mathematics, and related topics.

Areas of our research interest include Combinatorics and its applications; Spread spectrum communication; Signal processing; Image analysis for measurement; Networks; Sequence Design and its applications; GRID in scientific computing; Simulation techniques for complex systems; Computational biology; Security and management of computer system for e-Government; Blind source separation and independent component analysis, and their applications in acoustic signals and vital signs; Neural computing and brain-style signal processing; Optimization and machine learning; Time-reversal wave propagation in ergodic environment and its applications in acoustics, ultrasonics and telecommunications; Information theory and algorithmic complexity.

Faculty of the FCS laboratory teach Computer Literacy, Programming I, Algorithms and Data Structures, Advanced Algorithms, Digital Signal Processing, Introduction to Topology , SCCPs and other selective courses. Students join faculty research and also develop their own research themes. We participate in various research projects of JSPS, NIFS, RIKEN etc.

Granted research project: Grant-in-Aid from Ministry of Education, Culture, Sports, Science and Technology. Entitled "Study ternary sequence set having zero-correlation zone for periodic and Aperiodic correlation functions" Grant-in-Aid from Ministry of Education, Culture, Sports, Science and Technology. Entitled "Study on an Improvement of Security policy." Researches of real-time signal processing for blind source separation in convolutive mixing environment and real-time signal processing for independent component analysis, No.16500134, 2004 Grants-In-Aid for Scientific Research, JSPS.

Refereed Journal Papers

[sding-01:2005]	S. Ding, J Huang, D Wei, and A Cichocki. A Near Real-Time Approach for Convolutive Blind Source Separation. IEEE Transactions on Circuits and Systems, Part I: Regular Papers, 53(1):114-128, 2006.
	In this paper, we propose an algorithm for real-time signal processing of convolutive blind source separation (CBSS), which is a promising technique for acoustic source separation in a realistic environment, e.g., room/office or vehicle. First, we apply an overlap-and-save (sliding windows with overlapping) strategy that is most suitable for real-time CBSS processing; this approach can also aid in solving the permutation problem. Second, we consider the issue of separating sources in the frequency domain. We introduce a modified correlation matrix of observed signals and perform CBSS by diagonalization of the matrix. Third, we propose a method that can diagonalize the modified correlation matrix by solving a so-called normal equation for CBSS. One desirable feature of our proposed algorithm is that it can solve the CBSS problem explicitly, rather than stochastically, as is done with conventional algorithms. Moreover, a real-time separation of the convolutive mixtures of sources can be performed. We designed several simulations to compare the effectiveness of our algorithm with its counterpart, the gradient-based approach. Our proposed algorithm displayed superior convergence rates relative to the gradient-based approach. We also designed an experiment for testing the efficacy of the algorithm in real-time CBSS processing aimed at separating acoustic sources in realistic environments. Within this experimental context, the convergence time of our algorithms was substantially faster than that of the gradient-based algorithms. Moreover, our algorithm converges to a much lower value of the cost function than that of the gradient-based algorithm, ensuring better performance.
[sding-02:2005]	S. Ding, A Cichocki, J Huang, and D Wei. Blind Source Separation of Acoustic Signals in Realistic Environments Based on ICA in the Time-Frequency Domain. Journal of Pervasive Computing and Communications, 1(2):89-99, 2005.
	We present an approach for blind separation of acoustic sources produced from multiple speakers mixed in realistic room environments. We first transform recorded signals into the time-frequency domain to make mixing become instantaneous. We then separate the sources in each frequency bin based on an independent component analysis (ICA) algorithm. For the present paper, we choose the complex version of fixed-point iteration (CFPI), i.e., the complex version of FastICA, as the algorithm. From the separated signals in the time-frequency domain, we reconstruct output-separated signals in the time domain. To solve the so-called permutation problem due to the indeterminacy of permutation in the standard ICA, we propose a method that applies a special property of the CFPI cost function. Generally, the cost function has several optimal points that correspond to the different permutations of the outputs. These optimal points are isolated by some non-optimal regions of the cost function. In different but neighboring bins, optimal points with the same permutation are at almost the same position in the space of separation parameters. Based on this property, if an initial separation matrix for a learning process in a frequency bin is chosen equal to the final separation matrix of the learning process in the neighboring frequency bin, the learning process automatically leads us to separated signals with the same permutation as that of the neighbor frequency bin. In each bin, but except the starting one, by chosen the initial separation matrix in such a way, the permutation problem in the time domain reconstruction can be avoided. We present the results of some simulations and experiments on both artificially synthesized speech data and real-world speech data, which show the effectiveness of our approach.
[sding-03:2005]	W. Chen, D Wei, S Ding, M Cohen, H Wang, S Tokinoya, and N Takeda. A Scalable Mobile Phone-Based System for Multiple Vital Signs Monitoring and Healthcare. Journal of Pervasive Computing and Communications, 1(2):157-163, 2005.
	To meet the increasing needs for ubiquitous healthcare, a mobile phone-based system for monitoring multiple vital signs is under development. In this paper, design and implementation of the system architecture are described. The hierarchy of this system comprises three layers, which respectively handle multiple vital signs sensing, data/command communication via either wireless or wired means, and healthcare management. The fundamental basis of the sensing layer is a wearable cordless sensor device for monitoring vital signs without discomfort to the user during daily activities. The data communication layer performs bidirectional information exchange between the sensing layer and the management layer. The uppermost management layer conducts data mining and analysis for risk factors assessment and healthcare. Overall considerations of implementation method and prototype fabrication are outlined. Finally, applicability to a variety of real-world situations, and provision of customizable solutions not only for home healthcare but also for other vital signs-related domains (such as emergency rescue and safety guarantee) are discussed. Three of the most promising applications based upon this system are described.
[takafumi-01:2005]	Takafumi Hayashi. Binary Zero-Correlation Zone Sequence Set Construction Using a Primitive Linear Recursion. IEICE Transaction of Fundamentals., E89-A(2):633-638, 2006.
	In this letter, we present a new approach to the construction of a new binary ZCZ sequence set.
[takafumi-02:2005]	Takafumi Hayashi. A Class of Two-Dimensional Signal Having a Flat Power Spectrum and a Low Peak Factor. IEICE Transaction of Fundamentals., E89-A(2):494-502, 2006.
	In this letter, we present a new approach to the construction of low-peakfactor pseudo white noise sequence.
[takafumi-03:2005]	Takafumi Hayashi. Binary Zero-Correlation Zone Sequence Set Construction Using a Primitive Linear Recursion. IEICE Transaction of Fundamentals., E88-A(7):2034-2038, 2005.
	In this letter, we present a new approach to the construction of Binary ZCZ Sequence Set.

Referred Proceeding Papers

[sding-04:2005]	X. Zhu, W. Chen, S. Ding, H. Tsuchida, M. Cohen, and D Wei. Monitoring electrocardiograms via a mobile network system using cellular phones. In I. Kodama M. Hiraoka, S. Ogawa and H. Inoue, editors, Advances in Electrocardiology 2004, pages 700-704. The 31th International Congress on Electrocardiology, World Scientific, 2005.
	A tiny cordless sensor, 55 gram in weight and 117 �~ 36 �~16 mm3 in size, was used to acquire two-channel ECG from the coronal and vertical directions respectively on the thorax and transmit the ECG to a cellular phone via wireless Bluetooth protocol. In the cellular phone, heart rate can be reliably estimated from ECG signals with V-appli (embedded Java program for Vodafone cellular phone) software. When urgent events (e.g. arrhythmia, tachycardia) are detected, the ECG and location information related to such events can be uploaded to the server in the health care center for comprehensive analysis and forwarded to the doctor's cellular phone within 35 seconds
[takafumi-04:2005]	Takafumi Hayashi and Shinya Matsufuji. Sets of ZeroCorrelation Zone Sequence Pairs. In Proceedings of second IWSDA, pages 78-85. IEEE, Sept. 2005.
	A new classes ZCZ seqeunce pairs are proposed
[takafumi-05:2005]	Lukas Pichl, M. Arai, K. Hanabusa, and Takafumi Hayashi. Local Sequence Alignment Using Parallel Memory-Efficient Dynamic Programming. In Proceedings of 8th Joint Conference on Information Sciences, pages 1269-1272, July 2005.
	A new arrpoach to local sequence alignment is proposed.
[takafumi-06:2005]	Takafumi Hayashi, Shigeru Kanemoto, and Shigeki Tsunoyama. Ultrasonic Imaging Using a Ternary ZCZ Sequence Set. In Proc. 4th World Congress on Industrial Process Tomography, Sept. 2005.
	A new approach to ultrasonic imaging using a ternary ZCZ sequence set is proposed

Grants

[sding-05:2005]	S. Ding. Researches of real-time signal processing for blind source separation in convolutive mixing environment and real-time signal processing for independent component analysis, 2004-2006.
[takafumi-07:2005]	H Takafumi. Study ternary sequence set having zerocorrelation zone for periodic and Aperiodic correlation functions, 2004- 2005.
[takafumi-08:2005]	H Takafumi. Study on an Improvement of Security policy, 2003-2005.

Academic Activities

[sding-06:2005]	S. Ding, 2005. Institute of Electrical and Electronics Engineers (IEEE), Membership. Review Committee Member of ISCAS 2005 (2005 IEEE International Symposium on Circuits and Systems, Kobe, Japan)
[sding-07:2005]	S. Ding, 2005. IEEE Signal Processing Society, Membership. Reviewer for the IEEE Transactions on Signal Processing
[sding-08:2005]	S. Ding, 2005. Program Committee Member of CIT2005 (International Conference on Computer and Information Technology, Shanghai, China)
[sding-09:2005]	S. Ding, 2005. IEICE, Membership
[sding-10:2005]	S. Ding, 2005. The Association for Computing Machinery (ACM), Membership
[sding-11:2005]	S. Ding, 2005. The Acoustical Society of America (ASA), Membership
[sding-12:2005]	S. Ding, 2005. Review committee member candidate for Grants-In-Aid for Scientific Research projects, JSPS
[sding-13:2005]	S. Ding, 2005. Reviewer for the EURASIP Journal on Applied Signal Processing
[takafumi-09:2005]	Takafumi Hayashi, 2005. Reviewer of IEEE Signal Processing Letters
[takafumi-10:2005]	Takafumi Hayashi, 2005. Reviewer of IEEE Communication Letters
[takafumi-11:2005]	Takafumi Hayashi, 2005. Reviewer of ICC
[takafumi-12:2005]	Takafumi Hayashi, 2005. Reviewer of IEICE Transactions
[takafumi-13:2005]	Takafumi Hayashi, 2005. Reviewer of OE Magazine

Ph.D. and Other Theses

[takafumi-14:2005]	Takahiko Nitami. Graduation Thesis: Improvement of Virtual Environment Used for Measures to Fight Unknown Anti-virus Using Dynamic Heuristic Method, University of Aizu, 2006. Thesis Advisor: Takafumi Hayashi
[takafumi-15:2005]	Dai Nakajima. Graduation Thesis: Defense of Layers System Using Security-Enhanced Linux, University of Aizu, 2006. Thesis Advisor: Takafumi Hayashi
[takafumi-16:2005]	Sho Saito. Graduation Thesis: A Concept of Enterprise Security Policy, University of Aizu, 2006. Thesis Advisor: Takafumi Hayashi
[takafumi-17:2005]	Yasuharu Sugano. Graduation Thesis: How to manage the secret key, University of Aizu, 2006. Thesis Advisor: Takafumi Hayashi
[takafumi-18:2005]	Syuuji Henmi. Graduation Thesis: Security Planning Using Zachman Framework fore-governance, University of Aizu, 2006. Thesis Advisor: Takafumi Hayashi
[takafumi-19:2005]	Chihiro Kobayashi. Graduation Thesis: Enterprise Architecture for Security Planning, University of Aizu, 2006. Thesis Advisor: Takafumi Hayashi
[takafumi-20:2005]	Miho Matsuo. Education of Software Testing for Risk Reduction, University of Aizu, 2006. Thesis Advisor: Takafumi Hayashi
[takafumi-21:2005]	Kiichi Oose. Graduation Thesis: Research in Gapless Playing Music, University of Aizu, 2006. Thesis Advisor: Takafumi Hayashi
[takafumi-22:2005]	Norihisa Ootsubo. Graduation Thesis: The interface design in multi-agent stock simulation on SOARS, University of Aizu, 2006. Thesis Advisor: Takafumi Hayashi
[takafumi-23:2005]	Yoshimasa Yamamoto. Graduation Thesis: WLAN Security, University of Aizu, 2006. Thesis Advisor: Takafumi Hayashi

2007 THE UNIVERSITY OF AIZU ALL RIGHTS RESERVED