Three distortion reduction filters for radio-on-fiber systems are proposed and evaluated from the standpoint of improvements in in-band third order intermodulation (IM3) components (spurious components), insertion loss, temperature stability and so on. The basic filter configuration includes optical comb filter, RF (radiowave frequency) comb filter, and RF dual band rejection filter (DBRF). Experiments are conducted at 2 GHz band for frequency separation Δf=5 MHz and 100 MHz in the temperature range of -10 to +50. These filters can reduce IM3 components even in the saturation region, unlike conventional linearizers. An optical comb filter can reduce IM3 components more than 20 dB and noise level around 10 dB if its polarization controller is properly adjusted, but its insertion loss is large and stability against vibration is very poor. The proposed RF comb filter and RF-DBRF can reduce IM3 components by more than 20 dB and noise level by more than 3 dB. Their stability against vibration and temperature change is good, and insertion losses are 1-2 dB for Δf=100 MHz.

In speaker adaptation for speech synthesis, it is desirable to convert both voice characteristics and prosodic features such as F0 and phone duration. For simultaneous adaptation of spectrum, F0 and phone duration within the HMM framework, we need to transform not only the state output distributions corresponding to spectrum and F0 but also the duration distributions corresponding to phone duration. However, it is not straightforward to adapt the state duration because the original HMM does not have explicit duration distributions. Therefore, we utilize the framework of the hidden semi-Markov model (HSMM), which is an HMM having explicit state duration distributions, and we apply an HSMM-based model adaptation algorithm to simultaneously transform both the state output and state duration distributions. Furthermore, we propose an HSMM-based adaptive training algorithm to simultaneously normalize the state output and state duration distributions of the average voice model. We incorporate these techniques into our HSMM-based speech synthesis system, and show their effectiveness from the results of subjective and objective evaluation tests.

In this paper, we proposed an efficient coding method for digital hologram (fringe pattern) acquired with a CCD camera or by computer generation using multi-view prediction and MPEG video compression standard techniques. It processes each R, G, or B color component separately. The basic processing unit is a partial image segmented as the size of MN. Each partial image retains the information of the whole object. This method generates an assembled image for a column of the segmented and frequency-transformed partial images, which is the basis of the coding process. That is, a motion estimation and compensation technique of MPEG is applied between the reconstructed images from the assembled images with the disparities found during generation of assembled image and the original partial images. Therefore the compressed results are the disparity of each partial image to form the assembled image for the corresponding column, assembled image, and the motion vectors and the compensated image for each partial image. The experimental results with the implemented algorithm showed that the proposed method has NC (Normalized Correlation) values about 4% higher than the previous method at the same compression ratios, which convinced us that ours has better compression efficiency. Consequently, the proposed method is expected to be used effectively in the application areas to transmit or store in digital format the digital hologram data.

This paper presents a secure and simple content-based digital signature method for verifying the image authentication under JPEG, JPEG2000 compression and scaling based on a novel concept named lowest authenticable difference (LAD). The whole method, which is extended from the crypto-based digital signature scheme, mainly consists of statistical analysis and signature generation/verification. The invariant features, which are generated from the relationship among image blocks in the spatial domain, are coded and signed by the sender's private key to create a digital signature for each image, regardless of the image size. The main contributions of the proposed scheme are: (1) only the spatial domain is adopted during feature generation and verification, making domain transformation process unnecessary; (2) more non-malicious manipulated images (JPEG, JPEG2000 compressed and scaled images) than related studies can be authenticated by LAD, achieving a good trade-off of image authentication between fragile and robust under practical image processing; (3) non-malicious manipulation is clearly defined to meet closely the requirements of storing images or sending them over the Internet. The related analysis and discussion are presented. The experimental results indicate that the proposed method is feasible and effective.

A semi-supervised classification method is presented. A robust unsupervised spectral mapping method is extended to a semi-supervised situation. Our proposed algorithm is derived by linearization of this nonlinear semi-supervised mapping method. Experiments using the proposed method for some public benchmark data reveal that our method outperforms a supervised algorithm using the linear discriminant analysis for the iris and wine data and is also more accurate than a semi-supervised algorithm of the logistic GRF for the ionosphere dataset.

We investigate the enhancement of the optical nonlinearity and the limit of the improvement of the response speed in CdSxSe1-x microcrystallites by measuring the effective optical nonlinear cross section (σeff), the energy decay time (T1) and the dephasing time in two kinds of semiconductor microcrystallites of CdS0.12Se0.8 microcrystallites embedded in alkaline multi-component glasses (CdSSeMs) and CdSe microcrystallites embedded in SiO2 thin film (CdSeMs). As the average radius of CdSSeMs decreases from 10 to 1 nm, the values of σeff and T1 gradually change from 2.610-16 to 1.110-16 cm2 and from dozens picoseconds to 4 psec, respectively. The size dependence of CdSSEMs shows that the energy level structure in the microcrystallite with a radius of less than a few nanometers is a two-level system, in which σeff is proportional to T2. The carrier recombination time (τ) of CdSSeMs with the average radius of 1 nm is estimated to 2 psec. As the average radius of a CdS0.12Se0.8 microcrystallite decreases from 9 to 3 nm, the values of T2 gradually change from 640 to 230 fsec at 18 K, respectively. The size and temperature dependences of T2 for the CdSSeMs show that there is the discrepancy between the theory and the measured T2. The discrepancy showes the presence of the acoustic-phonon-assisted relaxation processes other than the pure-dephasing processes. It is indicated that T2 becomes long by reducing the excessive acoustic-phonon-assisted relaxation processes, and that the longer T2 might enhance σeff. We investigate the enhancement of σeff in CdSeMs by making T2 longer. The τ, σeff, and T2 of CdSeM an average radius of 3 nm are 40 psec, 4.510-15 cm2, and 150 fsec at room temperature. The σeff is ten times as large as that of CdSSeM sample at the same average radius and the enhancement of σeff can be considered to be caused by the longer T2.

We prepared transparent polymer films doped with π-conjugated organic dyes around a multimode silica fiber and observed very narrow fluorescence peaks as compared with the fluorescence in solution. The peak position showed no dependence on the excitation wavelength, indicating that it could not be explained by a whispering gallery mode in a medium with broad optical gain. The peaks can be explained by amplified spontaneous emissions (ASE) because the intensity depended linearly on the excitation intensity with a threshold. When the dye-doped film was formed on the portion of a fiber with the clad etched out and was excited by the polarized laser propagating inside the fiber core, we observed ASE peaks not of the dyes but of the optical fiber itself, suggesting the possibility that the dyes were oriented with their transition moment pointing parallel to the film surface. These fiber ASE peaks shifted to longer wavelength when we varied the excitation wavelength to shorter wavelength, which clearly ruled out the possibility of silicate Raman scattering as the origin.

This paper presents the characteristics and modeling of VoIP traffic for a real network. The new model, based on measured data, shows a significant difference from the previously proposed models in terms of parameters and their effects. It is found that the effects of background noise and ringing tones have essential influences on the model. The observed distributions of talkspurt and silent durations have long-tail characteristics and considerably differ from the existing models. An additional state called "Long burst", which represents the background noise at the talker's place, is added into the continuous-time Markov process model. The other three states, "Talk", "Short silence" and "Long silence", represent the normal behavior of the VoIP user. Models for conversational speech containing the communication during the dialogue are presented. In the case of the VoIP traffic aggregation, the simplified models, which neglect the conversation's interaction, are proposed. Depending on the occurrences of background noise during the speech, the model is classified as "noisy speech" or "noiseless speech". The measured data shows that the background noise typically increases the data rate by 60%. Simulation results of aggregated VoIP traffic indicate the self-similarity, which is analogous to the measured data. Results from the measurements support the fact that except the ringing duration the conversations from both the directions can be modeled in identical manner.

A well-defined test structure of organic static-induction transistor (SIT) having regularly sized nano-apertures in the gate electrode has been fabricated by colloidal lithography using 130-nm-diameter polystyrene spheres as shadow masks during vacuum deposition. Transistor characteristics of individual nano-apertures, namely 'nano-SIT,' have been measured using a conductive atomic-force-microscope (AFM) probe as a movable source electrode. Position of the source electrode is found to be more important to increase current on/off ratio than the distance between source and gate electrodes. Experimentally obtained maximum on/off ratio was 710 (at VDS = -4 V, VGS = 0 and 2 V) when a source electrode was fixed at the edge of gate aperture. The characteristics have been then analyzed using semiconductor device simulation by employing a strongly non-linear carrier mobility model in the CuPc layer. From device simulation, source current is found to be modulated not only by a saddle point potential in the gate aperture area but also by a pinch-off effect near the source electrode. According to the obtained results, a modified structure of organic SIT and an adequate acceptor concentration is proposed. On/off ratio of the modified organic SIT is expected to be 100 times larger than that of a conventional one.

Self-organized organic dye particles of micrometer and submicrometer size were prepared by utilizing a wetting/dewetting process of polar solvent on a hydrophilic glass substrate. The near-field scanning optical microscopy successfully identified near-field excited near-field fluorescence from single particles, however, the majority of the small particles with diameters around 2 µm or less did not show fluorescence under near-field observation. In contrast, far-field fluorescence, when excited by a polarized evanescent field, was observed, with the intensity depending on the excitation polarization, indicating that molecules' transition moment within dye particles was oriented parallel to the substrate surface. Single particle fluorescence spectrum consistently showed an identical sharp peak with a large redshift, indicating that the particles were composed of identical dye aggregates similar to J-aggregates. These observations suggest that the near-field at the probe tip was polarized parallel to the probe axis. Another observation, that molecules were oriented in a similar direction among adjacent particles, suggests that the dewetting process contributed to the alignment of the molecular orientation among adjacent particles, which further proves that the present specimen was formed by a self-organizing mechanism.

The concept of LR(k) validity is represented as an abstract interpretation of a refinement of the derivation semantics of a given grammar. Also the algorithm of LR(k) parsing is represented as an abstract interpretation of the refined semantics. Such representations of LR formalisms provide us with more intuitive and easier means by which to understand LR parsing.

With today's advances in peer-to-peer (P2P) techniques, a lot of non-document content has become searchable and usable. In the near future, since a huge amount of content will be distributed over the networks, not only index server searching but also P2P searching will become important because of its scalability and robustness. Typical P2P content searching services have some problems, such as low search precision ratio, significant increase in traffic and inundations of malicious content such as viruses. We propose a P2P content searching method in which a query is effectively forwarded only to peers that have indices of content semantically similar to the wanted content but not forwarded to the same peer repeatedly. It is based on the ideas of content addressable network (CAN) topology and a vector space method where vectors have a variable length. It maps non-document content to a vector space based on users' evaluations and manages the vector space or routes queries using the CAN topology control. The effectiveness of our method is shown by both analytical estimations and simulation experiments. The simulations clarified that our method is effective at improving the precision and recall ratios while reducing the amount of traffic compared with Gnutella flooding, the vector space method in which vector lengths are fixed (similar to the pSearch method), and Chord. In particular, when there was a lot of malicious content, our method exhibited a higher precision ratio than other methods.

Cell assembly is one of explanations of information processing in the brain, in which an information is represented by a firing space pattern of a group of plural neurons. On the other hand, effectiveness of neural network has been confirmed in pattern recognition, system control, signal processing, and so on, since the back propagation learning was proposed. In this study, we propose a new network structure with affordable neurons in the hidden layer of the feedforward neural network. Computer simulated results show that the proposed network exhibits a good performance for the back propagation learning. Furthermore, we confirm the proposed network has a good generalization ability.

Field assembly of optical connectors is demanded because of the wide use of optical fiber in telecommunications systems. We propose a new assembling techniques that enable us to assemble connectors anywhere quickly and cost effectively. The key points are an adhesive technique and a polishing technique. In this report, we focus mainly on our a new polishing machine, which is suitable for optical connector ends machining on-site. The machine which is small and light weight can finish optical connector ends easily in a short time with enough low cost.

We have developed an optical connector assembly method that allows the rapid on-site installation of an optical connector. To simplify this on-site assembly process we fabricated built-in parts that enable us to install the optical connector using pre-assembled optical connector parts. Moreover, we have established an advanced method for applying a solidifying agent that adheres to the inner wall of a ferrule flange. With our assembly method, we can complete on-site optical connector installation, other than the polishing process, in two steps, namely bonding agent application and fiber insertion.

A lexicon is an important linguistic resource needed for both shallow and deep language processing. Currently, there are few machine-readable Thai dictionaries available, and most of them do not satisfy the computational requirements. This paper presents the design of a Thai lexicon named the TCL's Computational Lexicon (TCLLEX) and proposes a method to construct a large-scale Thai lexicon by re-using two existing dictionaries and a large number of texts on the Internet. In addition to morphological, syntactic, semantic case role and logical information in the existing dictionaries, a sort of semantic constraint called selectional preference is automatically acquired by analyzing Thai texts on the web and then added into the lexicon. In the acquisition process of the selectional preferences, the so-called Bayesian Information Criterion (BIC) is applied as the measure in a tree cut model. The experiments are done to verify the feasibility and effectiveness of obtained selection preferences.

With advent of the ubiquitous network era and due to recent progress of III-V nanotechnology, the present III-V heterostructure microelectronics will turn into what one might call III-V heterostructure nanoelectronics, and may open up a new future in much wider application areas than today, combining information technology, nanotechnology and biotechnology. Instead of the traditional top-down approach, new III-V heterostructure nanoelectronics will be formed on nanostructure networks formed by combination of top-down and bottom-up approaches. In addition to communication devices, emerging devices include high speed digital LSIs, various sensors, various smart-chips, quantum LSIs and quantum computation devices covering varieties of application areas. Ultra-low power quantum LSIs may become brains of smart chips and other nano-space systems. Achievements of new functions and higher performances and their on chip integration are key issues. Key processing issue remains to be understanding and control of nanostructure surfaces and interfaces in atomic scale.

We extend a graph spectral method for extracting clusters from graphs representing pairwise similarity between data to hypergraph data with hyperedges denoting higher order similarity between data. Our method is robust to noisy outlier data and the number of clusters can be easily determined. The unsupervised method extracts clusters sequentially in the order of the majority of clusters. We derive from the unsupervised algorithm a semi-supervised one which can extract any cluster irrespective of its majority. The performance of those methods is exemplified with synthetic toy data and real image data.

We achieved first dynamic all-optical signal processing with a bandgap-engineered MZI SOA all-optical switch. The wide-gap Selective Area Growth (SAG) technique was used to provide multi-bandgap materials with a single step epitaxy. The maximum photoluminescence (PL) peak shift obtained between the active region and the passive region was 192 nm. The static current switching with the fabricated switch indicated a large carrier induced refractive index change; up to 14 π phase shift was obtained with 60 mA injection in the SOA. The carrier recovery time of the SOA for obtaining a phase shift of π was estimated to be 250-300 ps. A clear eye pattern was obtained in 2.5 Gbps all-optical wavelength conversion. This is the first all-optical wavelength conversion demonstration with a bandgap-engineered PIC with either selective area growth or quantum-well intermixing techniques.

Content-based publish/subscribe systems provide a useful alternative to traditional address-based communication due to their ability to decouple communication between participants. It has remained a challenge to design a scalable overlay supporting the complexity of content-based networks, while satisfying the desirable properties large distributed systems should have. This paper presents the design of Mirinae, a new structured peer-to-peer overlay mesh based on the interests of peers. Given an event, Mirinae provides a flexible and efficient dissemination tree minimizing the participation of non-matching nodes. We also present a novel ID space transformation mechanism for balancing routing load of peers even with highly skewed data, which is typical of the real world. Our evaluation demonstrates that Mirinae is able to achieve its goals of scalability, efficiency, and near-uniform load balancing. Mirinae can be used as a substrate for content-search and range query in other important distributed applications.