Showing papers by "University of Electro-Communications published in 1998"

Fuzzy regulators and fuzzy observers: relaxed stability conditions and LMI-based designs

Abstract: This paper presents new relaxed stability conditions and LMI- (linear matrix inequality) based designs for both continuous and discrete fuzzy control systems. They are applied to design problems of fuzzy regulators and fuzzy observers. First, Takagi and Sugeno's fuzzy models and some stability results are recalled. To design fuzzy regulators and fuzzy observers, nonlinear systems are represented by Takagi-Sugeno's (TS) fuzzy models. The concept of parallel distributed compensation is employed to design fuzzy regulators and fuzzy observers from the TS fuzzy models. New stability conditions are obtained by relaxing the stability conditions derived in previous papers, LMI-based design procedures for fuzzy regulators and fuzzy observers are constructed using the parallel distributed compensation and the relaxed stability conditions. Other LMI's with respect to decay rate and constraints on control input and output are also derived and utilized in the design procedures. Design examples for nonlinear systems demonstrate the utility of the relaxed stability conditions and the LMI-based design procedures.

Berry's Phase and Absence of Back Scattering in Carbon Nanotubes.

Abstract: The absence of back scattering in carbon nanotubes is shown to be ascribed to Berry's phase which corresponds to a sign change of the wave function under a spin rotation of a neutrino-like particle in a two-dimensional graphite. Effects of trigonal warping of the bands appearing in a higher order k · p approximation are shown to give rise to a small probability of back scattering.

Raman intensity of single-wall carbon nanotubes

Abstract: Using nonresonant bond-polarization theory, the Raman intensity of a single-wall carbon nanotube is calculated as a function of the polarization of light and the chirality of the carbon nanotube. The force-constant tensor for calculating phonon dispersion relations in the nanotubes is scaled from those for two-dimensional graphite. The calculated Raman spectra do not depend much on the chirality, while their frequencies clearly depend on the nanotube diameter. The polarization and sample orientation dependence of the Raman intensity shows that the symmetry of the Raman modes can be obtained by varying the direction of the nanotube axis, keeping the polarization vectors of the light fixed.

A unified approach to controlling chaos via an LMI-based fuzzy control system design

Abstract: This paper presents a unified approach to controlling chaos via a fuzzy control system design based on linear matrix inequalities (LMI's). First, Takagi-Sugeno fuzzy models and some stability results are recalled. To design fuzzy controllers, chaotic systems are represented by Takagi-Sugeno fuzzy models. The concept of parallel distributed compensation is employed to determine structures of fuzzy controllers from the Takagi-Sugeno fuzzy models, LMI-based design problems are defined and employed to find feedback gains of fuzzy controllers satisfying stability, decay rate, and constraints on control input and output of fuzzy control systems. Stabilization, synchronization, and chaotic model following control for chaotic systems are realized via the unified approach based on LMIs. An exact linearization (EL) technique is presented as a main result in the stabilization. The EL technique also plays an important role in the synchronization and the chaotic model following control. Two cases are considered in the synchronization. One is the feasible case of the EL problem. The other is the infeasible case of the EL problem. Furthermore, the chaotic model following control problem, which is more difficult than the synchronization problem, is discussed using the EL technique. Simulation results show the utility of the unified design approach based on LMIs proposed in this paper.

Two Spin-State Transitions in LaCoO 3

Abstract: Neutron-diffraction measurements have revealed a new anomalous thermal lattice expansion of LaCoO 3 near 500 K that indicates the existence of a second spin-state transition, in addition to the one previously established near 100 K. The anomalous expansion and the temperature dependence of the Co magnetic moments are successfully interpreted in a wide temperature range based on a simple model assuming low-spin (LS, S =0), intermediate-spin (IS, S =1), and high-spin (HS, S =2) states of Co atoms. The first spin transition, near 100 K, is from LS to IS, and the second, near 500 K, is from IS to a mixed state of IS and HS. The fitted model parameters indicate that the initially-large energy difference between IS and HS states decreases towards zero as the second transition proceeds. The large drop in resistivity associated with the latter transition appears to be correlated with the population of the HS state.

Statistical inference under multiterminal data compression

Abstract: This paper presents a survey of the literature on the information-theoretic problems of statistical inference under multiterminal data compression with rate constraints. Significant emphasis is put on problems: (1) multiterminal hypothesis testing, (2) multiterminal parameter estimation and (3) multiterminal pattern classification, in either case of positive rates or zero rates. In addition, the paper includes three new results, i.e., the converse theorems for all problems of multiterminal hypothesis testing, multiterminal parameter estimation, and multiterminal pattern classification at the zero rate.

Dynamic recrystallization under warm deformation of a 304 type austenitic stainless steel

Abstract: Warm (and hot) deformation of a 304 type austenitic stainless steel was studied in connection with microstructural developments in compression at temperatures of 873–1223 K (0.5–0.7 Tm) under strain rates of 10−4–10−1s−1. The two deformation domains can be categorized due to their different mechanical and microstructural behaviors. In the region of flow stresses lower than around 400 MPa, the deformation behaviors are typical for hot working accompanied with dynamic recrystallization (DRX). New grains are evolved mainly by dynamic bulging mechanism, which can be accelerated by the development of serrated grain boundaries and strain induced dislocation subboundaries. The relationship between dynamic grain sizes ranged from 2 to 7 μm and peak flow stress can be expressed by a power law function with a grain size exponent of −0.72. In contrast, in the region of flow stresses higher than 400 MPa, the deformation behaviors hardly depend on strain rate and temperature and so can be in the region of athermal deformation. The stress–strain curves under such warm deformation are similar to those affected only by dynamic recovery. The microstructures evolved at high strains are mainly characterized by the dense dislocation walls evolved in pancaked original grains, while grain boundary serration also takes place even at such warm deformation. Mechanisms of this microstructural evolution are discussed in combination with analysis of deformation mechanisms operating under warm deformation.

A wavelet transform-based ECG compression method guaranteeing desired signal quality

Abstract: This paper presents a new electrocardiogram (ECG) compression method based on orthonormal wavelet transform and an adaptive quantization strategy, by which a predetermined percent root mean square difference (PRD) can be guaranteed with high compression ratio and low implementation complexity.

Strain-induced grain evolution in polycrystalline copper during warm deformation

Abstract: The evolution mechanisms of dislocation microstructures and new grains at high strains of above 4 were studied by means of multiple compression of a polycrystalline copper (99.99 pct). Deformation was carried out by multipass compression with changing of the loading direction in 90 deg in each pass at temperatures of 473 K to 573 K (0.35 to 0.42 T m ) under a strain rate of 10−3 s−1. The flow stresses increase to a peak followed by a work softening accompanied mainly by dynamic recrystallization (DRX) at 523 K to 573 K. In contrast, the steady-state-like flow appears at 473K accompanied with the development of fine grains at strains as high as 4.2. The relationship of flow stress to the new grain size evolved can be expressed by a power law function with a grain size exponent of about −0.35, which is different from −0.75 for high-temperature DRX at above 0.5 T m . At 473 K, misorientations of deformation-induced dislocation subboundaries increase with increasing strain, finally leading to the evolution of new grains. It is concluded that the dynamic grain formation at 473 K cannot result from DRX, but from the evolution of deformation-induced dislocation subboundaries with high misorientations and, concurrently, the operation of dynamic recovery.

Magnetic properties of REMe0.5Mn0.5O3 (RE = Rare Earth Element, Me = Ni, Co)

Abstract: Magnetic properties of REMe 0.5 Mn 0.5 O 3 with Me = Ni and Co are investigated for a series of rare earth (RE) elements. In both systems with Me = Ni and Co, the Curie temperature ( T C ), below which the magnetic moments of Me 2+ and Mn 4+ allign ferromagnetically, decreases remarkably as RE goes from La to heavier elements; from 295 K for RE = La to 50 K for Lu with Me = Ni, and from 250 K for La to 95 K for Ho with Me = Co. The decrease of T C is interpreted as due to the bond angle (θ) dependence of the superexchange interactions between Me 2+ and Mn 4+ through O 2- ; T C is roughly linear to cos 2 θ as predicted by a simple theory [C. Boekema et al. : Int. J. Mag. 3 (1972) 341], but a distinct deviation from the linear relation is observed for the late RE elements. The magnetic moments of RE ions appears only in a low temperature region, typically below 30 K. Qualitative discussion on the exchange interactions involving RE is presented.

Operational capacity and pseudoclassicality of a quantum channel

Abstract: We explore some basic properties of coding theory of a general quantum communication channel and its operational capacity, including: 1) adaptive measurement with feedback code; 2) reconsideration of single-letterized capacity formula; and 3) pseudoclassicality of a channel.

An information-spectrum approach to capacity theorems for the general multiple-access channel

Abstract: The paper deals with the capacity problems for the general multiple-access channel, where the channel transition probabilities are arbitrary for every blocklength n. The approach used here, which is called the information-spectrum approach, is quite different from the standard typical-sequence and/or AEP techniques. The general formula for the capacity region for the general multiple-access channel is thus established. In order to examine the potentiality, we apply it to the mixed channel to obtain the formula for its capacity region. The case where input cost constraints are imposed is also considered.

A simple thermodynamic interpretation of Ce anomaly

Abstract: Thermodynamic condition necessary for the appearance of negative Ce anomaly has been calculated with the simplest assumption that cerianite (CeO2) is a unique species of Ce(IV) in water system and that hardly soluble nature of CeO2 is the direct cause of the Ce anomaly. Only negative Ce anomalies possess straightforward information on the chemical conditions responsible for the anomalies. The extent of Ce anomaly has been calculated on the basis that the maximum dissolved concentration of Ce is limited by the maximum of activity of Ce3+ (aCe3+) allowed by the formation of cerianite, which is determined mainly by pH and EH. In the calculation the activities of Ce in any solid phases are assumed to be unity. The Ce anomaly line exhibiting a certain magnitude of negative anomaly was invented and drawn in the EH-pH diagram. We then applied the Ce anomaly line to some natural samples (seawater, ground water, iron formation, etc.) showing negative Ce anomalies and found that the Ce anomalies fairly well reflect the EH-pH condition of the aqueous phase. In applying the Cc anomaly line to natural systems, the key parameter is the activity of Ce∗3+, not the concentration of Ce∗ (hypothetical Ce without Ce(IV) states). Too much credence, however, should not be given to the simple calculation, owing to the complication of the natural system and the lack of appropriate thermodynamic data.

An olfactory recognition model based on spatio-temporal encoding of odor quality in the olfactory bulb

Abstract: In order to study the problem how the olfactory neural system processes the odorant molecular information for constructing the olfactory image of each object, we present a dynamic model of the olfactory bulb constructed on the basis of well-established experimental and theoretical results. The information relevant to a single odor, i.e. its constituent odorant molecules and their mixing ratios, are encoded into a spatio-temporal pattern of neural activity in the olfactory bulb, where the activity pattern corresponds to a limit cycle attractor in the mitral cell network. The spatio-temporal pattern consists of a temporal sequence of spatial firing patterns: each constituent molecule is encoded into a single spatial pattern, and the order of magnitude of the mixing ratio is encoded into the temporal sequence. The formation of a limit cycle attractor under the application of a novel odor is carried out based on the intensity-to-time-delay encoding scheme. The dynamic state of the olfactory bulb, which has learned many odors, becomes a randomly itinerant state in which the current firing state of the bulb itinerates randomly among limit cycle attractors corresponding to the learned odors. The recognition of an odor is generated by the dynamic transition in the network from the randomly itinerant state to a limit cycle attractor state relevant to the odor, where the transition is induced by the short-term synaptic changes made according to the Hebbian rule under the application of the odor stimulus.

New grain formation during warm deformation of ferritic stainless steel

Abstract: Microstructural evolution accompanied by localization of plastic flow was studied in compression of a ferritic stainless steel with high stacking fault energy (SFE) at 873 K (≈0.5 Tm). The structure evolution is characterized by the formation of dense dislocation walls at low strains and subsequently of microbands and their clusters at moderate strains, followed by the evolution of fragmented structure inside the clusters of microbands at high strains. The misorientations of the fragmented boundaries and the fraction of high-angle grain boundaries increase substantially with increasing strain. Finally, further straining leads to the formation of new fine grains with high-angle boundaries, which become more equiaxed than the previous fragmented structure. The mechanisms operating during such structure changes are discussed in detail.

ISTP observations of plasmoid ejection: IMP 8 and Geotail

Abstract: IMP 8 and Geotail observations of traveling compression regions (TCRs) and plasmoids, respectively, are used to investigate plasmoid formation and ejection. One year of IMP 8 magnetometer measurements taken during the distant tail phase of the Geotail mission were searched for TCRs, which signal the release of plasmoids down the tail. A total of 10 such intervals were identified. Examination of the Geotail measurements showed that this spacecraft was in the magnetotail for only three of the events. However, in all three cases, clear plasmoid signatures were observed at Geotail. These plasmoids were observed at distances of X = −170 to −197 RE. The in situ plasma velocities in these plasmoids are found to exceed the time-of-flight speeds between IMP 8 and Geotail suggesting that some further acceleration may have taken place following release. The inferred lengths of these plasmoids, ∼27–40 RE, are comparable to the downtail distance of IMP 8. This indicates that TCR at IMP 8 can be caused by plasmoids forming not only earthward but also adjacent to or just tailward of the spacecraft. The closeness of IMP 8 to the point of plasmoid formation is confirmed by the small, ∼0–3 min, time delays between the TCR perturbation and substorm onset. In two of the plasmoid events, high-speed earthward plasma flows and streaming energetic particles were measured in the plasma sheet boundary layer surrounding the plasmoid along with large positive Bz at the leading edge of the plasmoid suggesting that the core of the plasmoid was “snow plowing” into flux tubes recently closed at an active distant neutral line. In summary, these unique two-point measurements clearly show plasmoid ejection near substorm onset, their rapid movement to the distant tail and their further evolution as they encounter preexisting X lines in the distant tail.

A sampling theorem for shift-invariant subspace

Abstract: A sampling theorem for regular sampling in shift-invariant subspaces is established. The sufficient-necessary condition for which it holds is found. Then, the theorem is modified to the shift sampling in shift-invariant subspaces by using the Zak transform. Finally, some examples are presented to show the generality of the theorem.

Relativistic dsp-model core potentials for main group elements in the fourth, fifth and sixth row and their applications

Abstract: We have developed advanced relativistic model core potentials (dsp-MCPs) for the fourth (Ga–Kr), fifth (In–Xe) and sixth-row (Tl–Rn) main-group elements, where the outermost core (n−1)d electrons were treated explicitly as well as the ns and np valence electrons. The remaining core electrons were replaced by dsp-MCPs. The major relativistic effects were incorporated into the dsp-MCPs at the level of Cowan and Griffin's quasi-relativistic Hartree–Fock method. We applied dsp-MCPs to calculate spectroscopic constants for the ground states of the rare-gas diatomic molecules Kr2 and Xe2. The results obtained by coupled pair approximation using atomic natural orbital (ANO) basis sets, in which the correlation of inner (n−1)d electrons was included as well as those of the valence ns and np electrons, give excellent agreement with experimental values.

Copy number control of IncIα plasmid ColIb-P9 by competition between pseudoknot formation and antisense RNA binding at a specific RNA site

Abstract: Replication of a low-copy-number IncIalpha plasmid ColIb-P9 depends on expression of the repZ gene encoding the replication initiator protein. repZ expression is negatively controlled by the small antisense Inc RNA, and requires formation of a pseudoknot in the RepZ mRNA consisting of stem-loop I, the Inc RNA target, and a downstream sequence complementary to the loop I. The loop I sequence comprises 5'-rUUGGCG-3', conserved in many prokaryotic antisense systems, and was proposed to be the important site of copy number control. Here we show that the level of repZ expression is rate-limiting for replication and thus copy number, by comparing the levels of repZ expression and copy number from different mutant ColIb-P9 derivatives defective in Inc RNA and pseudoknot formation. Kinetic analyses using in vitro transcribed RNAs indicate that Inc RNA binding and the pseudoknot formation are competitive at the level of initial base paring to loop I. This initial interaction is stimulated by the presence of the loop U residue in the 5'-rUUGGCG-3' motif. These results indicate that the competition between the two RNA-RNA interactions at the specific site is a novel regulatory mechanism for establishing the constant level of repZ expression and thus copy number.

Independent Spanning Trees with Small Depths in Iterated Line Digraphs.

Abstract: We show that the independent spanning tree conjecture on digraphs is true if we restrict ourselves to line digraphs. Also, we construct independent spanning trees with small depths in iterated line digraphs. From the results, we can obtain independent spanning trees with small depths in de Bruijn and Kautz digraphs that improve the previously known upper bounds on the depths.

Monoclinic Tungstates KDy(WO 4) 2 and KLu(WO 4) 2 - New χ( 3)-Active Crystals for Laser Raman Shifters

Abstract: Efficient high-order Stokes and anti-Stokes generation in the visible and near infrared (NIR) in monoclinic KDy(WO4)2 and KLu(WO4)2 1aser host crystals by stimulated Raman scattering (SRS) and Raman-induced four-wave mixing (RFWM) were observed at 300 K for the first time in the single-pass geometry under picosecond excitation. All scattering components were identified and connected with the SRS-active vibration modes of these tungstates.

EnhancedDesk: integrating paper documents and digital documents

Abstract: Digital media such as World Wide Web or CD-ROMs enable us to publish and transfer computer graphics, digital images, or audio data in ways that were not available for paper media. Yet, paper still has many advantages. It is easier to carry, strong enough to survive dropping or bending, and it offers highest resolution for printed text and images. We have developed an augmented desk top interface, EnhancedDesk, which utilizes computer vision technology. EnhancedDesk smoothly links paper documents and digital documents. EnhancedDesk users can manipulate digital information projected onto the desk manually. Applications that show the effectiveness of EnhancedDesk are given.

Fuzzy control based on quadratic performance function-a linear matrix inequality approach

Abstract: Presents an LMI approach to optimal fuzzy control based on a quadratic performance function. First, stability conditions are presented by relaxing the previous stability results. The relaxed stability conditions are represented in terms of LMIs. The optimal fuzzy controller design utilizing the relaxed stability conditions is proposed. The optimal fuzzy controller is designed by solving the minimization problem that minimizes the upper bound of a given quadratic performance function. Finally, a design example for the well-known nonlinear control benchmark problem, the TORA system, demonstrates the utility of the optimal fuzzy control based on a quadratic performance function.