Showing papers by "Nagoya Institute of Technology published in 1997"

Semiconductorlike Behavior of Electrical Resistivity in Heusler-type Fe 2 VAl Compound

Abstract: An anomalous negative temperature dependence of electrical resistivity has been observed in $({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{V}}_{x}{)}_{3}\mathrm{Al}$ alloys with V compositions up to $x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.35$. In particular, the Heusler-type ${\mathrm{Fe}}_{2}\mathrm{VAl}$ compound is found to be on the verge of magnetic ordering and to exhibit a semiconductorlike behavior with the resistivity reaching $3000\ensuremath{\mu}\ensuremath{\Omega}\mathrm{cm}$ at 2 K, in spite of the possession of a clear Fermi cutoff as revealed in photoemission valence-band spectra. A substantial mass enhancement deduced from specific heat measurements suggests that ${\mathrm{Fe}}_{2}\mathrm{VAl}$ is a possible candidate for a $3d$ heavy-fermion system.

Optical properties of wurtzite structure GaN on sapphire around fundamental absorption edge (0.78–4.77 eV) by spectroscopic ellipsometry and the optical transmission method

Abstract: Spectroscopic ellipsometry (SE) together with the optical transmission method is successfully used to determine the refractive index n and absorption coefficient α of undoped gallium nitride film over the spectral range of 0.78–4.77 eV of photon energy. The SE measurement is carried out at angle of incidence of 60° over the 1.5–4.77 eV energy range and optical transmission measurement over the 0.78–3.55 eV energy range. The refractive index n and absorption coefficient α obtained by both methods show unique results in the overlap wavelength region. Refractive index n is found to follow the Sellmeir dispersion relationship n2(λ)=2.272+304.72/(λ2−294.02) below the fundamental band edge. A free excitonic structure at the band is clearly observed at room temperature, with the transmission energy of free exciton at 3.44 eV, which is in reasonable agreement with the reported results.

A group synchronization mechanism for live media in multicast communications

Abstract: To support multicast communications for live media, the authors propose a group synchronization mechanism and enhance an intra-stream/inter-stream synchronization mechanism which they previously proposed for live media. The proposed method employs estimates of network delays for adjustment of the output timing among the destinations. The authors have implemented the mechanisms on a lip-synch experimental system. Live video of a speaker and his voice captured at a source are multicast, and then they are synchronized and output at the destinations. This paper also presents the system performance such as coefficient of variation of output interval, total pause time, mean square error of synchronization, average output rate, and average delay.

Structural Dependence of Aromatic Ring Stacking and Related Weak Interactions in Ternary Amino Acid−Copper(II) Complexes and Its Biological Implication

Abstract: Structures and stabilization due to stacking of ternary copper(II) complexes containing an aromatic amino acid (AA) and an aromatic diamine (DA), Cu(AA)(DA), have been investigated by potentiometric, spectroscopic, and X-ray diffraction methods. For the systems with AA = para-X-substituted l-phenylalanine (l-XPhe; X = H, NO2, OH, NH2) and DA = 2,2‘-bipyridine (bpy) or 1,10-phenanthroline (phen), the difference absorption spectra in the region 320−400 nm exhibited a peak assignable to the charge transfer interaction between the aromatic rings of DA and l-XPhe, the intensity being in the order NH2 > OH > H ≫ NO2 with respect to X. The stability constants of Cu(AA)(DA) determined for AA = dl-XPhe (X = F, Cl, Br) and l-XPhe (X = NH2, NO2, I) at 25 °C and I = 0.1 M (KNO3) indicated that stabilization of Cu(l-XPhe)(DA) relative to Cu(l-Ala)(en) (Ala = alanine; en = ethylenediamine) is in the order Br > OH > Cl ≈ NH2 > NO2 ≥ H ≥ F. The structures of [Cu(l-NH2Phe)(bpy)]NO3·H2O (1), [Cu(l-Tyr)(phen)]ClO4·2.5H2O (2...

Catalysis by Organic Solids. Stereoselective Diels−Alder Reactions Promoted by Microporous Molecular Crystals Having an Extensive Hydrogen-Bonded Network

Abstract: Anthracenebisresorcinol derivative 1 as an organic network material shows a novel catalysis in the solid state for the acrolein−cyclohexadiene Diels−Alder reaction. The suggested mechanism involves a catalytic cycle composed of sorption of the reactants in the cavities of polycrystalline host 1, preorganized intracavity reaction, and desorption of the product. The host also promotes stereoselective intracavity reactions for alkyl acrylates and cyclohexadiene but, in this case, not in a catalytic manner. Relevance of the present system as a functional organic analog of zeolites is discussed in light of the kinetics of respective elementary processes and the effects of pulverization of the catalyst thereupon as well as X-ray crystal structures.

A group synchronization mechanism for stored media in multicast communications

Abstract: This paper proposes a group synchronization mechanism, which synchronizes slave destinations with the master destination, for stored media in multicast communications. At the master and slave destinations, intra-stream and inter-stream synchronization mechanisms which were proposed by the authors are employed to output the master media stream and slave media streams synchronously. We achieve group synchronization by adjusting the output timing of the master media stream at each slave destination to that at the master destination. We also deal with traffic control by media scaling and control of joining an in-progress multicast group. Furthermore, the paper presents experimental results using an ATM network. It shows the validity of the mechanism and illustrates the influence of parameters on the system performance.

The Effect of MgO and Rare-Earth Oxide on Formation Behavior of Core-Shell Structure in BaTiO3

Abstract: The formation mechanism of the core-shell structure of a BaTiO3(BT)–MgO–Ho2O3-based system was studied. Mg reacted with BT at low temperatures and showed poor diffusivity compared with Ho. The core-shell structure was considered to be formed by the suppression of the diffusion of Ho into the core region by Mg. Also, replacement modes of Mg and Ho in perovskite were investigated. Lattice parameters were determined at temperatures higher than the Curie temperature in order to avoid crystal structure change. It was confirmed that Mg dissolved in Ti site, and Ho dissolved in both Ba and Ti sites. This indicates that Mg ions act as acceptors and Ho ions act as both donors and acceptors in the shell phase.

Ninf: A Network Based Information Library for Global World-Wide Computing Infrastructure

Abstract: Ninf is an ongoing global network-wide computing infrastructure project which allows users to access computational resources including hardware, software and scientific data distributed across a wide area network. Ninf is intended not only to exploit high performance in network parallel computing, but also to provide high quality numerical computation services and accesses to scientific database published by other researchers. Computational resources are shared as Ninf remote libraries executable at a remote Ninf server. Users can build an application by calling the libraries with the Ninf Remote Procedure Call, which is designed to provide a programming interface similar to conventional function calls in existing languages, and is tailored for scientific computation. In order to facilitate location transparency and network-wide parallelism, Ninf metaserver maintains global resource information regarding computational server and databases, allocating and scheduling coarse-grained computation for global load balancing. Ninf also interfaces with the WWW browsers for easy accessibility.

Evidence of water-cooperative proton conduction in silica glasses

Abstract: The effect of molecular water on proton conduction was quantitatively analyzed from conductivity measurements of silica glasses with and without water molecules. The activation energy for conduction linearly decreased with increasing logarithm of proton concentration for glasses containing only protons as charge carriers and as the logarithm of the product of proton and water concentration for glasses containing both proton and water. Electrical conduction in glasses containing both protons and water molecules is associated with proton hopping between hydroxyl and water molecules and its activation energy is related to the energy necessary for the dissociation of the proton from OH and ${\mathrm{H}}_{2}$O.

Current model-based sensorless drives of salient-pole PMSM at low speed and standstill

Abstract: For all the sensorless drives of the permanent magnet synchronous motor (PMSM), the major problem exists in their low-speed operation. This paper gives a solution to this problem by using a salient-pole PMSM. At low speeds, including zero speed, the rotor position and speed can be estimated by the current response of the voltage pulse, which is intermittently applied to the current minor loop. The current response is position dependent, because the winding inductance is a function of the rotor position. By using the relation between the current response and the rotor position, the basic algorithm of the sensorless drive can be developed. Experimental results from a six-pole 1500 RPM 1.5 kW test motor have proved the stable sensorless drive characteristics below 50 RPM, including zero speed, under 0%-100% loaded conditions.

Glutathione status and reactive oxygen generation in tissues of young and old exercised rats

Abstract: The effects of exercise on the generation of active oxygen species and radical-scavenging capacity were studied in physically active and sedentary young and old rats. Exercise increased the hydroxyl radical content in all tissues of physically active young rats, except in the plasma. In old rats, the basal level of the radical increased significantly in plasma, heart, and skeletal muscles, but decreased in liver; and physical activity decreased it to that of young rats in most cases. With exercise, the content of reduced glutathione increased in plasma, heart, and skeletal muscles of young rats, whereas that of oxidized glutathione markedly decreased in liver and increased in brain and white gastrocnemius muscle. The total glutathione levels in these tissues changed in a similar way, indicating that glutathione was released from the pool in the liver. In rats allowed to run voluntarily for 5 weeks, the effects were more pronounced than in the sedentary rats. The ratio of reduced to total glutathione, which indicates the capacity to reduce glutathione, increased in plasma, heart, and soleus muscle of sedentary young rats after exercise, and increased further in those undergoing physical activity. In old rats, the reduced glutathione level increased in plasma, heart, liver, and brain, even though the total decreased. These results suggest that physical activity enhances the endogenous ability to defend against oxidative stress. In old rats, even though glutathione synthesis is decreased, the regenerating capacity seems to be increased in order to compensate for the increased oxidative stress.

Functional Self-Assembly of Hydrogen-Bonded Networks. Construction of Aromatic Stacks and Columns and Cavity-Size Control via Flexible Intercalation of 1D Chains Having Orthogonal Aromatic Substituents

Abstract: Anthracene−monoresorcinol derivative 1 forms hydrogen-bonded poly(resorcinol) 1D chains, which self-assemble via interpenetration or intercalation of the orthogonal anthracene (A) substituents. Guest-binding in the resulting cavities leads to either, depending on the guests (G, aromatic or aliphatic), an alternate ···A·G·A·G··· (monomeric) or an ···A·A·G·G··· (dimeric) lattice pattern. The monomeric lattices show a remarkable linear-alkyl vs branched-alkyl selectivity in the guest-binding. The dimeric lattices are characterized by their exclusive emission of excimer fluorescence. Self-assembly of the present 1D chains is thus functional and also flexible and dynamic; removal, addition, and exchange of guest molecules readily occur in the solid states.

Unification of robust design and goal programming for multiresponse optimization—a case study

Abstract: Fixing the levels of input process parameters to meet a required specification of output is a common process quality control problem. Especially when the output has many quality characteristics, and each of these quality characteristics has to satisfy a given specification, difficulties may arise. One such problem was encountered in an injection moulding process. This process was optimized using Taguchi's Robust Design methodology. Details of the process, problems encountered and outcome of optimization are presented in this paper. The optimization study using Taguchi's methodology revealed that the optimum conditions obtained for one response are not completely compatible with those of other responses. So trade-offs were made in selection of levels for factors using engineering judgement. This increases the uncertainty in the decision making process. In this paper, an approach is presented to optimize multiresponses simultaneously using goal programming in conjunction with Taguchi's methodology. Details of modelling, analysis and inferences obtained with relevance to the case are presented. This study revealed that the optimum conditions obtained using goal programming in conjuction with Taguchi's methodology have better goal attainment properties compared to Robust design. To understand goal attainment behaviour of output characteristics for various process conditions, a detailed sensitivity analysis was also conducted. The outcome of this analysis is also discussed in this paper. © 1997 John Wiley & Sons, Ltd.

On a common quadratic Lyapunov function for widely distant systems

Abstract: A sufficient condition concerning the construction of a common quadratic Lyapunov function for widely distant linear systems is presented. The condition is set on a mutual relation matrix whose size is just equal to the number of the coefficient matrices.

Two conditions concerning common quadratic Lyapunov functions for linear systems

Abstract: Concerning a pair of linear systems, some triangle conditions for the existence of a common quadratic Lyapunov function are presented in this paper. These conditions are derived from a criterion for judging the semipositiveness of a linear map defined on symmetric matrices.

Adsorption mechanism of trivalent metal ions on chelating resins containing iminodiacetic Acid groups with reference to selectivity.

Abstract: The adsorption equilibria of seven trivalent metal ions (M3+: Sc3+, Y3+, La3+, Fe3+, Al3+, Ga3+, and In3+) on chelating resins containing iminodiacetic acid groups (-LH2) were studied. Adsorption curves, measured under the conditions of metal ions in excess against chelating groups, directly indicated the metal-to-ligand ratio of the complexes formed in the resin phase. Iron and group 13 metal ions were adsorbed as (-L)2HM, while group 3 metal ions were adsorbed as (-L)3H3M and (-L)2HM. The adsorption constants for (-L)2HM found for all the metal ions were well correlated with the formation constants of iminodiacetate complexes in aqueous solutions. The actual adsorption of group 3 metal ions was significantly enhanced beyond that expected from this correlation because of the formation of (-L)3H3M. This is why the selectivity in the adsorption of trivalent metal ions differs from that in the complexation of iminodiacetate in aqueous solutions. The effects of anions and the number of iminodiacetic acid gr...

A New Technique of Compound Semiconductor Deposition from an Aqueous Solution by Photochemical Reactions

Abstract: CdS films were successfully formed on a glass substrate in an aqueous solution containing S2O32- and Cd2+ ions by photochemical reaction. S2O32- ions in the growth solution absorb ultra-violet light of wavelengths shorter than about 300 nm, and the excited S2O32- ions supply sulfur atoms and electrons to the metal ions such as Cd2+. Thus, the formation reaction of the sulfide semiconductor occurs in the only illuminated region. Photochemically deposited CdS thin films were polycrystalline of hexagonal structure. The composition of the films became stoichiometric by the annealing at temperatures higher than 300° C.

Diffuse reflectance infrared Fourier transform spectral study of the interaction of 3-aminopropyltriethoxysilane on silica gel. Behavior of amino groups on the surface

Abstract: Three silica gel sample systems, modified with 3-aminopropyltriethoxysilane (APTS), were prepared by sequentially sampling the reaction mixture at various time intervals, and the diffuse reflectance infrared Fourier transform (DRIFT) spectra of these samples were measured in the regions 2700–3500 and 1300–2000 cm-1. The IR bands observed at 1597 and 1629–1633 cm-1 were assigned to the deformation modes of NH2 and NH 3 + groups, respectively. The intensities of these two bands are dependent on both the APTS concentration used in the preparation and the reaction time. The results are summarized as follows. For the sample systems in which smaller APTS concentration were used, most of the NH2 groups of the aminopropyl segments are converted into the NH 3 + groups on the surface, showing that the SiO- H+ NH2- type structure is predominantly stabilized on the surface of the silica gel. As the APTS concentration in the reaction mixture increases, the population of NH2 groups in the silane layer coated onto the surface increases. Interpretation of the CH stretch region further suggests that cyclic structures may be formed on the surface as a consequence of the formation of NH 3 + groups.

Pressurized flow‐driven capillary electrochromatography using ion exchange resins

Abstract: Capillary electrochromatography using cation and anion exchange resins under pressurized flow is demonstrated to be applied to the separation of charged solutes, such a lanthanide ions. The typical variation of elution order for the mixture of sulfite, sulfate, and thiosulfate ions, the reduction and extension of elution times due to the application of high voltage, and the simultaneous separation of cations and anions are demonstrated. A minor component appears by shifting the elution time of a major component while applying a high electric field. The electric resistance of the column was measured under electrochromatographic conditions, and its dependence on the applied voltage has been discovered. From the relationship between elution times and applied voltage, the sum of electrophoretic mobility of an ion and electroosmotic mobility is estimated for landthanide cations. The capacity factor in electrochromatography is found to depend, to some extent, on the potential gradient. © 1997 John Wiley & Sons, Inc. J Micro Sep9: 347–356, 1997

Effect of electrochemically deposited apatite coating on bonding of bone to the HA-G-Ti composite and titanium

Abstract: The surfaces of hydroxyapatite-glass-titanium (HA-G-Ti) functionally gradient composite and titanium bars were treated with electrochemical apatite deposition, and a cathodic current was applied at 62 degrees C in a solution containing calcium and phosphate ions. Specimens with and without the electrochemical surface treatment were implanted in the femurs of Japanese white rabbits. The rabbits were sacrificed at 3, 6, and 9 weeks after implantation, and the bonding strengths of bone to these specimens were determined by a pull-out method. At 3 and 6 weeks after implantation the specimens with the electrochemical surface treatment showed larger values for the Weibull modulus and characteristic strengths than those of untreated specimens, whereas there was no remarkable difference in the results at 9 weeks. Especially the pull-out strengths of surface-treated specimens were significantly larger than the untreated ones at 3 weeks after implantation. Scanning electron microscopy and Fourier transform infrared absorption spectroscopy of the specimen surface after implantation demonstrated that formation of new bone was enhanced by the electrochemical surface treatment. It can be concluded that the electrochemical surface treatment undoubtedly contributes to the early stage fixation between bone and implant.