Showing papers by "Tokyo Institute of Technology published in 1976"

Selection of the order of an autoregressive model by Akaike's information criterion

Abstract: SUMMARY The asymptotic distribution is obtained of the order of regression selected by Akaike's information criterion in autoregressive models. The asymptotic quadratic risks of estimates of regression parameters are evaluated when the order is selected by this method. Some results of computational experiments are given.

Stochastic Approximation and Recursive Estimation

Abstract: An extrusion head for an extrudable material, such as a food product dough, which is to be formed into a special shape, such as a pretzel configuration. The head includes a die and associated parts which are of such character and construction that portions of the extruded material will differ in width and thickness from other portions.

Experiments on transition to turbulence in an oscillatory pipe flow

Abstract: Experiments on transition to turbulence in a purely oscillatory pipe flow were performed for values of the Reynolds number Rδ, defined using the Stokes-layer thickness δ = (2ν/ω)½ and the cross-sectional mean velocity amplitude U, from 19 to 1530 (or for values of the Reynolds number Re, defined using the pipe diameter d and U, from 105 to 5830) and for values of the Stokes parameter λ = ½d(ω/2ν)½ (ν = kinematic viscosity and ω = angular frequency) from 1·35 to 6·19. Three types of turbulent flow regime have been detected: weakly turbulent flow, conditionally turbulent flow and fully turbulent flow. Demarcation of the flow regimes is possible on Rλ, λ or Re, λ diagrams. The critical Reynolds number of the first transition decreases as the Stokes parameter increases. In the conditionally turbulent flow, turbulence is generated suddenly in the decelerating phase and the profile of the velocity distribution changes drastically. In the accelerating phase, the flow recovers to laminar. This type of partially turbulent flow persists even at Reynolds numbers as high as Re = 5830 if the value of the Stokes parameter is high.

Control of unstable mechanical system Control of pendulum

Abstract: This paper relates to the design of a control system for a mechanical system which contains an unstable mode and to an experiment for demonstrating that the control theory may be applied to practical real systems. In this paper the object treated is the control of the pendulum-cart system, which has been studied by many control theorists and engineers as an inverted pendulum problem, and a composite control system is designed not only to stabilize the inverted pendulum but to swing the pendulum from the natural pendent position up to the inverted position, which is actually made. The experimental results are presented.

Flow and Bed Topography in Curved Open Channels

Abstract: Mean flow characteristics and bed shear distributions in uniformly curved open channels have been studied theoretically, and the results are compared with experiments and field observations. Next, an equation which expresses the variation of transverse bed profile is derived by considering an equilibrium of forces acting on a sand particle. It is shown that the magnitude of the secondary flow and the transverse bed slope determine the direction of sand movement. The numerical solution of the bed variation with time are compared with experiments, and it is concluded that the model employed here describes the bed variation fairly well. The stable profile of the bed is obtained analytically, and from this result the maximum depth of scour which occurs at the outer banks is calculated.

Minimal order state observers for bilinear systems

Abstract: This paper considers a minimal order state observer for a bilinear system. The given observer is an extension of one for a linear system and can be designed without considering inputs because the estimation error is made to be independent of inputs. The necessary condition for the existence of a minimal order observer and a standard form of a bilinear system satisfying this condition are presented. A standard form of a minimal order state observer is also obtained and the design procedure of this observer is shown. As an example, the observer of a d.c. motor is designed.

Kinematic Control of Active Cord Mechanism with Tactile Sensors

Abstract: A biomechanical study of living systems suggests us some interesting mechanisms which enable an organism to carry out specific functions. Among various organisms, the authors deal with the organism having a slender configuration and making active and flexible winding motions with muscles attached along the body. In spite of the simple shape, it performs miscellaneous functions which have never been realized in an artificial mechanism. The authors call this type of organism as Active Cord-Mechanism (abbreviated as ACM) and have been studying its motion, control and other problems associated with an engineering application. The basic locomotive motion of ACM on an even ground has already been realized in a snake-like shape. In this paper, some of the problems to develope this locomotive ACM into a more intelligent machine are discussed. First, the installation of tactile sensors is discussed and the biological principle of lateral inhibition is shown to be useful for controlling the ACM with tactile sensors. Second, the efficient and smooth controlling principle is proposed which the authors call the modified first order data hold. Finally, by the ACM mechanical model with tactile sensors and reconstructed controller, more intelligent locomotive experiments have been made, to demonstrate that the locomotion by detecting the obstacle in labyrinth, or the propulsion by pushing a fixed object have been successfully accomplished. Thus the authors believe that this study solves some of the controlling problems of locomotive ACM to develope as an intelligent machine.

Modulational Instability and Envelope-Solitons for Nonlinear Alfven Waves Propagating along the Magnetic Field in Plasmas

Abstract: The modulational instability and envelope-solitons are analyzed for the Alfven waves propagating along the static magnetic field in cold collisionless plasmas, using the modified nonlinear Schrodinger equation previously derived by the authors. The modulational instability occurs in the left-hand circularly polarized Alfven wave (left Alfven wave) for a small amplitude but does not for an amplitude larger than the critical value. On the other hand, the instability never occurs in the right-hand circularly polarized Alfven wave (right Alfven wave). When the modulational instability does not occur, the rarefactive and compressive envelope-solitons exist in the left Alfven wave and the two types of the rarefactive envelope-solitons exist in the right Alfven wave.

Induction of chromosome motion in the glycerol‐isolated mitotic apparatus: nucleotide specificity and effects of antidynein and myosin sera on the motion

Abstract: Chromosome motion in glycerol-isolated mitotic apparatus (MA) of sea urchin and starfish eggs was investigated with respect to nucleotide specificity and the effects of antisera against tryptic fragment (Fragment A) of flagellar dynein and starfish egg myosin. The motion was highly specific for ATP. GTP, ITP, CTP, UTP, and ADP caused no displacement of the chromosomes towards the poles. The anti-Fragment A serum completely inhibited chromosome motion in the MA of the sea urchin egg, while antiserum against starfish egg myosin as well as its γ-globulin fraction did not inhibit the motion in the isolated MA of the starfish egg, suggesting that chromosome motion depends upon dynein-microtubule but not upon myosin-actin interaction. In addition, colchicine completely suppressed the chromosome motion in vitro.

Ferroelectricity in RbLiSO4

Abstract: In RbLiSO 4 , dielectric measurements and microscopic observations have revealed successive phase transitions at 166, 188, 202 and 204°C with rising temperature. Ferroelectricity has been found along the a axis in the phase between 166 and 188°C. Further a ferrielectric behavior is found in this phase, when a field higher than about 20 kV/cm is applied.

Random Ordered Phase Characteristic of Quenched Mixtures of Ising Spins

Abstract: A new ordered phase, tentatively called “random ordered phase” (ROP) is proposed in the quenched Ising spin system in which ferro- and antiferromagnetic exchange integrals exist. In the ROP each spin points to the same direction as the molecular field which is either up or down and is altered from site to site according as the various situations of surroundings. The phase transition is characterized by “random magnetization” and “random susceptibility”, whose expressions are given.

Crystallographic and Dielectric Properties in the Solid Solution Systems Pb(Fe 2/3 W 1/3 )O 3 -Pb(Mg 1/3 Ta 2/3 )O 3 and Pb(MgW) 1/2 O 3 -Pb(FeTa) 1/2 O 3

Abstract: It was found that complete solid solutions are formed in the systems of Pb(Fe 2/3 W 1/3 )O 3 -Pb(Mg 1/3 Ta 2/3 )O 3 and Pb(MgW) 1/2 O 3 -Pb(FeTa) 1/2 O 3 .Pb(Fe 2/3 W 1/3 )O 3 and Pb(Mg 1/3 Ta 2/3 )O 3 are disordered perovskite type ferroelectrics, nevertheless the ordered arrangement of ions in the octahedral positions is formed to some degree in a certain region of intermediate composition . In the case of Pb(MgW) 1/2 O 3 -Pb(FeTa) 1/2 O 3 , the state changes from antiferro- to ferro-electric at about 70 mole percent of Pb(FeTa) 1/2 O 3 . The X-ray intensity of superlattice reflections was analyzed based on two different models. To confirm the ferro- or antiferro-electric behavior, the permittivity was measured in Pb(MgW) 1/2 O 3 -Pb(FeTa) 1/2 O 3 System under applying d.c. bias field, and forced transition from antiferro to ferro-electric state was observed to occur in the biasing cycle.

Composition and Morphology of Hydrated Tricalcium Silicate

Abstract: Hardened C3S paste cured for 1 year at 20°C was examined to confirm the composition and the morphology of hydrated tricalcium silicate. A new technique was used in which the samples for scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) were etched in 1% HNO3-alcohol or in glycerol-alcohol (4:6 by volume). After the surface was etched in 1% HNO3-alcohol, SEM clearly showed the difference in texture in the outer and inner C-S-H products. The existence of a zonal texture within the inner C-S-H products was shown, in addition to the unreacted core; particles 0.1 to 0.2 μm in diameter were observed. After free CH extraction with glycerol-alcohol, two new types of C-S-H grains could be identified. One type has a smooth surface, which seems to be produced from C3S grains trapped within the growing CH crystals in the early stage of hydration, the C/S mol ratio for these being >3. The other type is covered with many acicular outer C-S-H gel hydration products and has a C/S mol ratio >3.

Discussion on the mechanism of photodoping

Abstract: The photo-enhanced reaction between metallic silver and vitreous chalcogenides is known as “photodoping”. Based on a series of experimental results, a model for photodoping was proposed. It was assumed in this model, that a junction barrier at the silver-chalcogenide interface worked for separating photocarriers. Holes are captured by metallic silver, and electrons are trapped by active or loosely bound chalcogen atoms after travel toward the interior of a glass layer. The Coulomb attraction field between ions thus formed is large enough to overcome the kinetic barrier in the process of silver diffusion. The square root dependence for the growth of the photodoped depth with exposure time has been explained in the light of this proposed model.

Ground State and Phase Transition in the Quenched Random Mixture of Ferro-Antiferromagnets

Abstract: The energy and spin pair-correlation in the ground state and the phase transition for a random mixture of the ferro-antiferromagnets in a quenched Ising system have been investigated by a new idea based on a division of the lattice into elementary units. The effects of the loop proper to the each lattices have been explicity considered. It is demonstrated that the transition temperatures are intimately related to the ground-state energy. Monte Carlo simulations performed on the square lattice are also reported.

The Ground State of the Optical Polaron in the Strong-Coupling Case

Abstract: The next lowest order term of the ground state energy has its origin in lowering of frequencies of phonons localized around the polaron. An eigenvalue equation is derived, the solution of which gives phonon eigenmodes and frequencies in the presence of the polaron. Several eigenvalues are obtained by numerical integration. From the results, the ground state energy is estimated as \(E_{0}/\hbar\omega_{0}{=}-0.108513\alpha^{2}-2.836+O(1/\alpha^{2})\), where ω 0 is the frequency of the optical phonon and α is the electron-phonon coupling constant. The numerical value of the effective mass is 0.0227019α 4 .