Ranking fuzzy numbers is one of very important research topics in fuzzy set theory because it is a base of decision-making in applications. However, fuzzy numbers may not be easily ordered into one sequence according to their magnitudes because they represent uncertain values. When two fuzzy numbers overlap with each other, a fuzzy number may not be considered absolutely larger than the other. That is, even when a fuzzy number may be considered larger than the other, it may also be considered smaller than the other. It means that for a given set of fuzzy numbers, several ranking sequences possibly exist. However, most of the existing ranking methods produce only one ranking sequence. They ignore other possible sequences due to the overlap between fuzzy numbers. We propose a ranking method which generates possible ranking sequences of given fuzzy numbers. Our method takes a viewpoint from users, and uses it for evaluation of fuzzy numbers. Fuzzy numbers will be ranked based on the evaluations and a fuzzy set of sequences of fuzzy numbers will be produced as a ranking results. Numeric examples and comparisons with other methods are also presented.

This paper focuses on flow control in high-speed networks. Each node in a network handles its local traffic flow on the basis of only the information it is aware of, but it is preferable that the decision-making of each node leads to high performance of the whole network. To this end, we investigate the relationship between the flow control mechanism of each node and network performance. We consider the situation in which the capacity of a link in the network is changed but individual nodes are not aware of this. Then we investigate the stability and adaptability of the network performance, and discuss an appropriate flow control model on the basis of simulation results.

Handovers are occasionally required for LEO (Low Earth Orbit) satellite systems, since the satellites are always moving. Handovers, however, generally cause some degradation of communication quality. Some LEO systems have a feature of two types of satellites in terms of the direction of their orbits and the handover between satellites of different types may lead to a large change in the path between the service satellites used for the communication. Thus, the degradation can be generally large especially in the case of handovers between different type satellites. As such, best handover plan should be derived so that the number of handovers should be made smallest to minimize the degradation of the communication quality. In this paper, such optimization problems are formulated in relation to the handovers and their solutions are proposed to actualize the optimization of handover plans for LEO satellite systems with two types of satellites.

Direct conversion techniques commonly used for the transmitter in basestation rely on analog performance of the quadrature modulator. In this paper, simulated results show that imperfections in analog quadrature modulation--gain and phase error and dc offset--have a devastating effect on digital predistortion for power amplifier linearization circuits. We construct compensation circuit to remove these errors, and conduct an experiment. The imbalance errors are compensated by using the output spectrum of modulator. The image spurious (-56.74 dBm) with gain, phase and the dc offset spurious (-43.83 dBm) are reduced to -93.21 dBm and -93.56 dBm, respectively. These experimental results illustrate that modulation errors can be eliminated.

The recent real time systems have the needs of system expandability with heterogeneous functions and operations. High assurance system is very important for such systems. In order to realize the high assurance system, we research the autonomous step-by-step construction technique based on assurance evaluation. In this paper we propose the average functional reliability as the best index to indicate the assurance performance for system construction. We also propose the autonomous step-by-step construction technique to decide the construction sequence to maximize the assurance performance.

This paper assesses the media synchronization quality of recovery control schemes from asynchrony, which are referred to as reactive control schemes here, in terms of objective and subjective measures. We deal with four reactive control techniques: skipping, discarding, shortening and extension of output duration, and virtual-time contraction and expansion. We have carried out subjective and objective assessment of the media synchronization quality of nine schemes which consist of combinations of the four techniques. The paper makes a comparison of media synchronization quality among the schemes. It also clarifies the relations between the two kinds of quality measures.

In this paper, a new Hierarchical Sum of Double Difference metric, HSDD, is introduced. It is shown, as opposed to conventional Sum of Absolute Difference (SAD) metric, how this zerotree coding aware metric can jointly constrain the motion vector searching for both temporal and spatial (quad-tree) directions under multiresolution motion estimation framework. The reward from the temporal-spatial co-optimization concept of HSDD is that fewer bits are spent later for describing the isolated zeros. The embedded wavelet video coder using HSDD metric was tested with a set of video sequences and the compression performance seems to be promising.

We propose a normalization scheme of syntactic structures using a binary phrase structure grammar with composite labels. The normalization adopts binary rules so that the dependency between two sub-trees can be represented in the label of the tree. The label of a tree is composed of two attributes, each of which is extracted from each sub-tree, so that it can represent the compositional information of the tree. The composite label is generated from part-of-speech tags using an automatic labelling algorithm. Since the proposed normalization scheme is binary and uses only part-of-speech information, it can readily be used to compare the results of different syntactic analyses independently of their syntactic description and can be applied to other languages as well. It can also be used for syntactic analysis, which performs higher than the previous syntactic description for Korean corpus. We implement a tool that transforms a syntactic description into normalized one based on this proposed scheme. It can help construct a unified syntactic corpus and extract syntactic information from various types of syntactic corpus in a uniform way.

We propose a frequency stabilization system for laser diodes (LDs), in which the electrical feedback loop response can be determined using an on-line genetic algorithm (GA) so as to attain lower LD frequency noise power within the specific Fourier frequency range of interest. At the initial stage of the stabilization, the feedback loop response has been controlled through GA, manipulating the proportional gain, integration time, and derivative time of conventional analog PID controller. Individuals having 12-bit chromosomes encoded by combinations of PID parameters have converged evolutionarily toward an optimal solution providing a suitable feedback loop response. A fitness function has been calculated for each individual in real time based on the power spectral density (PSD) of the frequency noise. The performance of this system has been tested by stabilizing a 50 mW visible LD. Long-term (τ > 0.01 s) frequency stability and its repeatability have been improved.

This paper describes an experimental study on resonant properties of the plasma-wave field-effect transistors (PW-FET's). The PW-FET is a new type of the electron devices, which utilizes the plasma resonance effect of highly dense two-dimensional conduction electrons in the FET channel. Frequency tunability of plasma-wave resonance in the terahertz range was experimentally investigated for sub 100-nm gate-length GaAs MESFET's by means of laser-photo-mixing terahertz excitation. The measured results, including the first observation of the third-harmonic resonance in the terahertz range, however, fairly deviate from the ideal characteristics expected for an ideal 2-D confined electron systems. The steady-state electronic charge distribution in the MESFET channel under laser illumination was analyzed to study the effect of insufficient carrier confinement on the frequency tunability. The simulated results support the measured results. It was clarified that an ideal heterostructure 2-D electron confinement is essential to assuring smooth, monotonic frequency tunability of plasma-wave resonance.

Nominalization is a linguistic phenomenon in which events usually described in terms of clauses are expressed in the form of noun phrases. Extracting event structures is an important task in text mining applications. To achieve this goal, clauses are parsed and the argument structure of main verbs are extracted from the parsed results. This kind of preprocessing has been commonly done in the past research. In order to extract event structure from nominalized phrases as well, we need to establish a technique to transform nominalized phrases into clauses. In this paper, we propose a method to transform nominalized phrases into clauses by using corpus-based approach. The proposed method first enumerates possible predicate/argument structures by referring to a nominalized phrase (noun phrase) and makes their ranking based on the frequency of each argument in the corpus. The algorithm based on this method was evaluated using a corpus consisting of 24,626 aviation safety reports in English and it achieved a 78% accuracy in transformation. The algorithm was also evaluated by applying a text mining application to extract events and their cause-effect relations from the texts. This application produced an improvement in the text mining application's performance.

The segregation of non-magnetic phases such as borosilicate and Cr was investigated by crystallization behavior during the surface and bulk crystallization of Co-based amorphous alloys. The concentration of metalloids (B and Si) determined the extent of grain boundary segregation of borosilicate glass during surface crystallization. During the bulk crystallization of (Co75Cr25)0.8Si5B15 amorphous alloy, solute rejection of Cr resulted in the nucleation of Cr-deficient ferromagnetic crystals and non-magnetic σ-phase was subsequently precipitated along the grain boundary. These results show that crystallization process, i.e. nucleation and growth can be controlled to optimize the microstructure to reduce media noises in Co-based recording media.

Several 2 nm seed layers were sputtered to increase coercivity (Hc) and anisotropy (Ku) of CoCrPt/Ti perpendicular recording media. Among them 2 nm Ag seed layer was very effective to increase Hc of (Co78Cr22)100-xPtx/Ti (x = 14, 20). However, the effect was more pronounced when (Co78Cr22)100-xPtx/Ti became thinner. In addition α[=4π(dM/dH)Hc] decreased when the Ag layer was used. The film thickness below which the seed Ag layer was effective was reduced with decreasing Pt content. However, the Ag seed layer did not promote (0002) texture of Ti and CoCrPt layers. Domain size was reduced when the Ag seed layer was used. The effects of Ag seed layer are thought to be due to change of exchange constant of the grains, for which the grain boundary plays an important role. Effects of film thickness and Pt content can also be explained successfully by the variation of exchange constant due to grain boundary. Some experimental evidence as well as crude mode for exchange constant variation are given.

In this paper, a quasi-synchronous code-division multiple-access (QS-CDMA) is investigated for application in the reverse link of a microcellular or indoor mobile communication environment. In a QS-CDMA system, the relative time delay between the signals of different users is normally restricted within a few chips. Generalized orthogonal (GO) codes added with guard chips are employed as the spreading sequences in this paper and the strict timing error restrictions for BPSK and M-QAM modulation schemes are derived based on the correlation properties of GO code set which determines the multiple access interference (MAI). The results reveal that the system employing GO code set with bigger GO zone can tolerate more serious timing error, and higher order modulation schemes require stricter synchronization. Based on the system model presented, the BER performance for BPSK and M-QAM is evaluated by Gaussian Approximation (GA) and Monte Carlo simulation. The system capacity in terms of acquirable total bit rates are also evaluated, revealing that if system synchronization error is limited within the GO zone, M-QAM scheme can be utilized to improve the system capacity.

Although there has been a great deal of research on automatic summarization, most methods rely on statistical methods, disregarding relationships between extracted textual segments. We propose a novel method to extract a set of comprehensible sentences which centers on several key points to ensure sentence connectivity. It features a similarity network from documents with a lexical dictionary, and spreading activation to rank sentences. We show evaluation results of a multi-document summarization system based on the method participating in a competition of summarization, TSC (Text Summarization Challenge) task, organized by the third NTCIR project.

Automatic text summarization has the goal of reducing the size of a document while preserving its content. Generally, producing a summary as extracts is achieved by including only sentences which are the most topic-related. DOCUSUM is our summarization system based on a new topic keyword identification method. The process of DOCUSUM is as follows. First, DOCUSUM converts the content words of a document into elements of a context vector space. It then constructs lexical clusters from the context vector space and identifies core clusters. Next, it selects topic keywords from the core clusters. Finally, it generates a summary of the document using the topic keywords. In the experiments on various compression ratios (the compression of 30%, the compression of 10%, and the extraction of the fixed number of sentences: 4 or 8 sentences), DOCUSUM showed better performance than other methods.

This paper proposes a statistical method of acquiring knowledge about the abbreviation possibility of some of multiple adnominal phrases. Our method calculates weight values of multiple adnominal phrases by mutual information based on the strength of relation between the adnominal phrases and modified nouns. Among adnominal phrases, those having relatively low weight values are deleted. The evaluation of our method by experiments shows that precision attains about 84.1% and recall attains about 59.2%, respectively.

We developed a multiple document summarization system GOLD. This system generates a single summary from relevant newspaper articles with any summarization rate specified by a user. GOLD is incorporated a number of methods to summarize. In particular, some methods for sentence reduction are useful to shorten each sentence. As a result, it increased the number of outputted sentences which include important information. We participated in task B of NTCIR3 TSC2 to evaluate this system. GOLD exhibits a good performance in content-based evaluation which suggests that summarization methods employed by GOLD are promising for practical use.

In most cases of distributed memory computations, node programs are executed on processors according to the owner computes rule. However, owner computes rule is not best suited for irregular application codes. In irregular application codes, use of indirection in accessing left hand side array makes it difficult to partition the loop iterations, and because of use of indirection in accessing right hand side elements, we may reduce total communication by using heuristics other than owner computes rule. In this paper, we propose a communication cost reduction computes rule for irregular loop partitioning, called least communication computes rule. We partition a loop iteration to a processor on which the minimal communication cost is ensured when executing that iteration. Then, after all iterations are partitioned into various processors, we give global vs. local data transformation rule, indirection arrays remapping and communication optimization methods. The experimental results show that, in most cases, our approaches achieved better performance than other loop partitioning rules.

Optical Character Reader (OCR) incorrect recognition is a serious problem when searching for OCR-scanned documents in databases such as digital libraries. In order to reduce costs, this paper proposes fuzzy retrieval methods for English text containing errors in the recognized text without correcting the errors manually. The proposed methods generate multiple search terms for each input query term based on probabilistic automata which reflect both error-occurrence probabilities and character-connection probabilities. Experimental results of test-set retrieval indicate that one of the proposed methods improves the recall rate from 95.96% to 98.15% at the cost of a decrease in precision from 100.00% to 96.01% with 20 expanded search terms.