Showing papers by "Tokyo Institute of Technology published in 1995"

Optical Switching and Image Storage by Means of Azobenzene Liquid-Crystal Films

Abstract: Liquid crystals are promising materials for optical switching and image storage because of their high resolution and sensitivity. Azobenzene liquid crystals (LCs) have been developed, in which azobenzene moieties play roles as both mesogens and photosensitive chromophores. Azobenzene LC films showed a nematic phase in trans isomers and no LC phase in cis isomers. Trans-cis photoisomerization of azobenzene with a laser pulse resulted in a nematic-to-isotropic phase transition with a rapid optical response of 200 microseconds.

The Seasonal Cycle over the Tropical Pacific in Coupled Ocean Atmosphere General Circulation Models

Abstract: The seasonal cycle over the tropical Pacific simulated by 11 coupled ocean–atmosphere general circulation models (GCMs) is examined. Each model consists of a high-resolution ocean GCM of either the tropical Pacific or near-global means coupled to a moderate- or high-resolution atmospheric GCM, without the use of flux correction. The seasonal behavior of sea surface temperature (SST) and eastern Pacific rainfall is presented for each model. The results show that current state-of-the-art coupled GCMs share important successes and troublesome systematic errors. All 11 models are able to simulate the mean zonal gradient in SST at the equator over the central Pacific. The simulated equatorial cold tongue generally tends to be too strong, too narrow, and extend too far west. SSTs are generally too warm in a broad region west of Peru and in a band near 10°S. This is accompanied in some models by a double intertropical convergence zone (ITCZ) straddling the equator over the eastern Pacific, and in others...

Rectangle-packing-based module placement

Abstract: The first and the most critical stage in VLSI layout design is the placement, the background of which is the rectangle packing problem: Given many rectangular modules of arbitrary size, place them without overlapping on a layer in the smallest bounding rectangle. Since the variety of the packing is infinite (two- dimensionally continuous) many, the key issue for successful optimization is in the introduction of a P-admissible solution space, which is a finite set of solutions at least one of which is optimal. This paper proposes such a solution space where each packing is represented by a pair of module name sequences. Searching this space by simulated annealing, hundreds of modules could be successfully packed as demonstrated. Combining a conventional wiring method, the biggest MCNC benchmark ami49 is challenged.

Atomic‐scale formation of ultrasmooth surfaces on sapphire substrates for high‐quality thin‐film fabrication

Abstract: The atomically ultrasmooth surfaces with atomic steps of sapphire substrates were obtained by annealing in air at temperatures between 1000 and 1400 °C. The terrace width and atomic step height of the ultrasmooth surfaces were controlled on an atomic scale by changing the annealing conditions and the crystallographic surface of substrates. The obtained ultrasmooth surface was stable in air. The topmost atomic structure of the terrace was examined quantitatively by atomic force microscopy and ion scattering spectroscopy as well as a theoretical approach using molecular dynamics simulations.

Speech parameter generation from HMM using dynamic features

Abstract: This paper proposes an algorithm for speech parameter generation from HMMs which include the dynamic features. The performance of speech recognition based on HMMs has been improved by introducing the dynamic features of speech. Thus we surmise that, if there is a method for speech parameter generation from HMMs which include the dynamic features, it will be useful for speech synthesis by rule. It is shown that the parameter generation from HMMs using the dynamic features results in searching for the optimum state sequence and solving a set of linear equations for each possible state sequence. We derive a fast algorithm for the solution by the analogy of the RLS algorithm for adaptive filtering. We also show the effect of incorporating the dynamic features by an example of speech parameter generation.

Cyclin B interaction with microtubule-associated protein 4 (MAP4) targets p34cdc2 kinase to microtubules and is a potential regulator of M-phase microtubule dynamics.

Abstract: We previously demonstrated (Ookata et al., 1992, 1993) that the p34cdc2/cyclin B complex associates with microtubules in the mitotic spindle and premeiotic aster in starfish oocytes, and that microtubule-associated proteins (MAPs) might be responsible for this interaction. In this study, we have investigated the mechanism by which p34cdc2 kinase associates with the microtubule cytoskeleton in primate tissue culture cells whose major MAP is known to be MAP4. Double staining of primate cells with anti-cyclin B and anti-MAP4 antibodies demonstrated these two antigens were colocalized on microtubules and copartitioned following two treatments that altered MAP4 distribution. Detergent extraction before fixation removed cyclin B as well as MAP4 from the microtubules. Depolymerization of some of the cellular microtubules with nocodazole preferentially retained the microtubule localization of both cyclin B and MAP4. The association of p34cdc2/cyclin B kinase with microtubules was also shown biochemically to be mediated by MAP4. Cosedimentation of purified p34cdc2/cyclin B with purified microtubule proteins containing MAP4, but not with MAP-free microtubules, as well as binding of MAP4 to GST-cyclin B fusion proteins, demonstrated an interaction between cyclin B and MAP4. Using recombinant MAP4 fragments, we demonstrated that the Pro-rich C-terminal region of MAP4 is sufficient to mediate the cyclin B-MAP4 interaction. Since p34cdc2/cyclin B physically associated with MAP4, we examined the ability of the kinase complex to phosphorylate MAP4. Incubation of a ternary complex of p34cdc2, cyclin B, and the COOH-terminal domain of MAP4, PA4, with ATP resulted in intracomplex phosphorylation of PA4. Finally, we tested the effects of MAP4 phosphorylation on microtubule dynamics. Phosphorylation of MAP4 by p34cdc2 kinase did not prevent its binding to microtubules, but abolished its microtubule stabilizing activity. Thus, the cyclin B/MAP4 interaction we have described may be important in targeting the mitotic kinase to appropriate cytoskeletal substrates, for the regulation of spindle assembly and dynamics.

Peg1/Mest imprinted gene on chromosome 6 identified by cDNA subtraction hybridization.

Abstract: Parthenogenesis in the mouse is embryonic lethal partly because of imprinted genes that are expressed only from the paternal genome. In a systematic screen using subtraction hybridization between cDNAs from normal and parthenogenetic embryos, we initially identified two apparently novel imprinted genes, Peg1 and Peg3. Peg1 (paternally expressed gene 1) or Mest, the first imprinted gene found on the mouse chromosome 6, may contribute to the lethality of parthenogenones and of embryos with a maternal duplication for the proximal chromosome 6. Peg1/Mest is widely expressed in mesodermal tissues and belongs to the alpha/beta hydrolase fold family. A similar approach with androgenones can be used to identify imprinted genes that are expressed from the maternal genome only.

Continuous mixing of crystal mush and replenished magma in the ongoing Unzen eruption

Abstract: Zoning profiles of magnetite phenocrysts in the successively effused dacite of the ongoing Unzen eruption from 1991 wereanalyzed to estimate the time scale of magma mixing. The dacite was formed by mixing of relatively high- and low-temperature ( T ) end-member magmas. The magnetite phenocrysts derived from the low- T magma are reversely zoned by the mixing with high- T magma. A diffusion calculation for reequilibration of the reverse zonings gives the time interval from magma mixing to quenching. For the mixed dacite erupted from May 1991 to May 1993, the typical diffusion time was estimated to be a few months regardless of the effused sequence for 2 yr. This indicates that the mixing was continuous during the effusion. The invariability of the other mixing signatures, such as the thickness of reaction rims around biotite phenocrysts, also supports the continuous mixing model. Low-T end-member magma is estimated by mass-balance calculation to be a crystal-rich mush of dacitic composition. These observations lead to a model wherein the highly crystallized remnant magma of the preceding activity has been mixed with the newly injected hot magma of similar bulk composition just prior to the effusion. The proposed mechanism implies that this type of magma mixing is an inevitable process in periodically erupting polygenetic volcanoes.

Arbitrary path tracking control of articulated vehicles using nonlinear control theory

Abstract: Designs a path tracking controller for an articulated vehicle (a semitrailer-like vehicle) using time scale transformation and exact linearization. The proposed controller allows articulated vehicles to follow arbitrary paths consisting of arcs and lines, while they are moving forward and/or backward. The experimental result of the 8-shaped path tracking control of the articulated vehicle moving backward is also presented. >

Critical behavior in gravitational collapse of radiation fluid: A renormalization group (linear perturbation) analysis

Abstract: A scenario is presented, based on renormalization group (linear perturbation) ideas, which can explain the universality and scaling observed in a numerical study of gravitational collapse of radiation fluid. In particular, it is shown that the critical exponent $\ensuremath{\beta}$ and the largest Lyapunov exponent $\mathrm{Re}\ensuremath{\kappa}$ of the perturbation is related by $\ensuremath{\beta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\mathrm{Re}\ensuremath{\kappa}{)}^{\ensuremath{-}1}$. We find the relevant perturbation mode numerically, and obtain a fairly accurate value of the critical exponent $\ensuremath{\beta}\ensuremath{\simeq}0.35580192$, also in agreement with that obtained in numerical simulation.

Time Frequency Analysis of Dispersive Waves by Means of Wavelet Transform

Abstract: A new approach is presented for investigating the dispersive character of structural waves. The wavelet transform is applied to the time-frequency analysis of dispersive waves. The flexural wave induced in a beam by lateral impact is considered. It is shown that the wavelet transform using the Gabor wavelet effectively decomposes the strain response into its time-frequency components. In addition, the peaks of the time-frequency distribution indicate the arrival times of waves. By utilizing this fact, the dispersion relation of the group velocity can be accurately identified for a wide range of frequencies.

Replication factor encoded by a putative oncogene, set, associated with myeloid leukemogenesis

Abstract: DNA replication of the adenovirus genome complexed with viral core proteins is dependent on the host factor designated template activating factor I (TAF-I) in addition to factors required for replication of the naked genome. Recently, we have purified TAF-I as 39- and 41-kDa polypeptides from HeLa cells. Here we describe the cloning of two human cDNAs encoding TAF-I. Nucleotide sequence analysis revealed that the 39-kDa polypeptide corresponds to the protein encoded by the set gene, which is the part of the putative oncogene associated with acute undifferentiated leukemia when translocated to the can gene. The 41-kDa protein contains the same amino acid sequence as the 39-kDa protein except that short N-terminal regions differ in both proteins. Recombinant proteins, which were purified from extracts of Escherichia coli, expressing the proteins from cloned cDNAs, possessed TAF-I activities in the in vitro replication assay. A particular feature of TAF-I proteins is the presence of a long acidic tail in the C-terminal region, which is thought to be an essential part of the SET-CAN fusion protein. Studies with mutant TAF-I proteins devoid of this acidic region indicated that the acidic region is essential for TAF-I activity.

Cluster-based text categorization: a comparison of category search strategies

Abstract: Text categorization can be viewed asaprocessof catego~ search, in which one or more categories for a testdocument are searchedfor by using given training documents with known categories. In this paper a cluster-based search with a probabilistic clustering algorithm is proposed and evaluated on two data sets. The “efficiency, effectiveness, and noise tolerance of this search strategy were confirmed to be better than those of a full search, a category-based search, and a cluster-based search with nonprobabilistic clustering.

Record low-threshold index-guided InGaAs/GaAlAs vertical-cavity surface-emitting laser with a native oxide confinement structure

Abstract: An index-guided InGaAs/GaAlAs vertical-cavity surface-emitting laser with a native oxide confinement structure has been proposed and fabricated. A record threshold current of 70 µA was achieved with a 5 µm-diameter core device. The proposed structure provides strong electrical and optical confinements. Also a reduction in nonradiative recombination and an improvement in the thermal resistance can be expected.

Theoretical aspects of fuzzy control

Abstract: Partial table of contents: Identification of Linguistic Fuzzy Models (R. Yager & D. Filev) System Stability and the Fuzzy Controller (J. Buckley) Typology of Fuzzy Controllers (L. Foulloy & S. Galichet) Modeling of Control Functions by Fuzzy Controllers (P. Bauer, et al.) Optimal Strategy of Switching Reasoning Methods in Fuzzy Control (M. Smith & V. Kreinovich) Considerations of Hierarchical Fuzzy Control (C. de Silva) Fuzzy Relational Control (W. Pedrycz) Some Research Directions in Fuzzy Control (D. Driankov, et al.) Function Approximation with Additive Fuzzy Systems (B. Kosko & J. Dickerson) Index.

The XY-centring algorithm for the dual LMI problem: a new approach to fixed-order control design

Abstract: Many fixed-order suboptimal control problems with stability, performance and robustness specifications can be reduced to a search for a matrix X > 0 satisfying a linear matrix inequality (LMI) while X −1 satisfies another LMI. This paper defines a certain class of these problems we shall call the ‘dual LMI problem’, and a computational algorithm to solve our dual LMI problem is given. Properties and limitations of the algorithm are discussed in comparison with the existing algorithm (the min/max algorithm). An extension to optimal control problems is provided. Numerical examples for the fixed-order stabilization problem and the static output feedback linear quadratic optimal control problem demonstrate the applicability of the proposed algorithm.