Subharmonic modulation distortions in semiconductor lasers with optical feedback

Experimental studies of subharmonic modulation distortions of semiconductor lasers with optical feedback are described. These distortions were found to exhibit almost resonant frequency characteristics and threshold behaviour against the modulation frequency and its depth, respectively. It was inferred that they would be excited by parametric interactions caused by some laser diode parameter changes due to modulation.     

Structure and electrical conductivity of graphite fibers prepared by pyrolysis of cyanoacetylene

Highly electroconductive graphite fibers are prepared by the pyrolysis (CVD) of cyanoacetylene on the surface of carbon fibers, followed by heat treatment. Many thin graphite strata, cylindrically layered and scrolled around an axial core of the original carbon fiber, are observed. The lattice constant C₀ of the graphite fiber obtained from cyanoacetylene and heat-treated at 3000 °C is 6.712° (002), which is smaller than that of a graphite fiber from benzene. The magnetoresistance of graphite fibers obtained from cyanoacetylene is as high as 800% (4.2K, 15 kG) (HTT 3300 °C), while that of graphite fibers obtained from benzene is around 150%. Measurements of Raman scattering and X-ray diffraction also show that cyanoacetylene forms more highly graphitized fiber than benzene. Cyanoacetylene is a good starting material for synthesizing graphite. The room temperature conductivity is as high as 1.8 × 10⁴ S/cm for fiber heat treated at 3250 °C. Treatment of the graphite fiber by fuming nitric acid increases the conductivity up to 1.3 sx 10⁵ S/cm in less than 10 min. Upon exposure of the nitrated fiber to air at ambient temperature, the conductivity decreases slightly. After this slight decrease, the conductivity is stable for at least 90 days.     

Real time application of simultaneous estimation theory for parameters and state to one-dimensional heat conduction

This paper applies filtering theory of the parameters and states of a distributed system to one-dimensional heat conduction in order to obtain information on the real time application of nonlinear estimation theory. This involves a trial to study a simple and fast algorithm for the state estimation of power reactors limited to a small number of sensors by noisy observations. The authors estimated the heat transfer coefficients and the transient temperature profile in a copper rod simultaneously in real time by using a small computer, NOVA 3/12, where the parameter and state of the heat conduction-type P.D.E. could serve as a simplified alternative to the nuclear constant and power profile. The authors also examined the feasibility of a nonlinear filter provided for simultaneous estimation, considering unknown parameters as alternative state variables. The filter tested converged during the sampling period and generated reasonable estimates of the parameter and state from noisy observations with a small number of sensors and at a discrete number of times.     

Study on the detection of prion protein in food products by a competitive enzyme-linked immunosorbent assay

We developed a competitive enzyme-linked immunosorbent assay (ELISA) to detect prion protein contained in materials derived from cattle, aiming at establishing a method to detect abnormal prion protein (PrPSc) in food products. Rabbit polyclonal antibodies were raised against bovine prion peptides. Using these antibodies, we have established a competitive ELISA that is capable of detecting recombinant bovine prion protein (rBoPrP) in the range of 12 to 1,200 ng and we used it to determine prion protein contents in bovine cerebral cortex. This assay system was evaluated by spiking food products with various amounts of rBoPrP. The determination gave 2-fold higher values in minced meat homogenates and lower values in large intestine homogenates than the values expected from the spiked amounts. This assay provides a simple determination method of spiked rBoPrP, and therefore is expected to be useful for investigating sample pretreatment methods.     

Loss mechanisms in piezoelectrics: how to measure different losses separately

Losses in piezoelectrics are considered in general to have three different mechanisms: dielectric, mechanical, and piezoelectric losses. This paper deals with the phenomenology of losses first, then how to measure these losses separately in experiments. We found that heat generation at off-resonance is caused mainly by dielectric loss tan delta' (i.e., P-E hysteresis loss), not by mechanical loss, and that a significant decrease in mechanical Qm with an increase of vibration level was observed in resonant piezoelectric ceramic devices, which is due to an increase in the extensive dielectric loss, not in the extensive mechanical loss. We propose the usage of the antiresonance mode rather than the conventional resonance mode, particularly for high power applications because the mechanical quality factor QB at an antiresonance frequency is larger than QA at a resonance frequency.     

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Feedforward and Feedback Dynamic Trot Gait Control for Quadruped Walking Vehicle

To realize dynamically stable walking for a quadruped walking robot, the combination of the trajectory planning of the body and leg position (feedforward control) and the adaptive control using sensory information (feedback control) is indispensable. In this paper, we propose a new body trajectory, the 3D sway compensation trajectory, for a stable trot gait; we show that this trajectory has a lower energy consumption than the conventional sway trajectory that we have proposed. Then, for the adaptive attitude control method during the 2-leg supporting phase, we consider four methods, that is, a) rotation of body along the diagonal line between supporting feet, b) translation of body along the perpendicular line between supporting feet, c) vertical swing motion of recovering legs, and d) horizontal swing motion of recovering legs; we then describe how we verify the stabilization efficiency of each method through computer simulation, stabilization experimentation, and experimenting in walking on rough terrain using the quadruped walking robot, TITAN-VIII.     

Epenthetic vowels in Japanese: A perceptual illusion?

In 4 cross-linguistic experiments comparing French and Japanese listeners, we found that the phonotactic properties of Japanese (a reduced set of syllable types) induce Japanese listeners to perceive "illusory" vowels inside consonant clusters in vowel-consonant-consonant-vowel (VCCV) stimuli. In Experiments 1 and 2, a continuum of stimuli ranging from no vowel (e.g., ebzo) to a full vowel between the consonants (e.g., ebzo) was used. Japanese, but not French participants, reported the presence of a vowel [u] between consonants, even in stimuli with no vowel. A speeded ABX discrimination paradigm was used in Experiments 3 and 4 and revealed that Japanese participants had trouble discriminating between VCCV and VCuCV stimuli. French participants, in contrast, had problems discriminating items that differed in vowel length ( ebuzo vs ebuuzo), a distinctive contrast in Japanese but not French. It is concluded that models of speech perception have to be revised to account for phonotactically based assimilations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)