Atsushi Osa

Detection of Physiological Parameters without Any Physical Constraints in Bed Using Sequential Image Processing.

Physiological parameters, specifically, body movement and respiratory waveform, were observed utilizing an original image sequence processing system. In this study, sequential image processing methods were used to observe both patients with acute myocardial infarction and normal subjects in bed. The results of standard differential image processing and a gradient-based method were strongly correlated with body movement of the subject. Furthermore, the respiratory waveform was detected using the gradient-based method. This image sequence processing system appears very promising for the evaluation of physical activity without any physical constraints in bed.

Evaluation of Body Motion by Optical Flow Analysis

For quantitative evaluation of body motion, a fully noncontact and unconstraining monitoring method was developed by introducing image sequence analysis. A spatiotemporal local optimization method was applied to determine optical flow in the image sequence. The optical flow visualized the apparent velocity field of the entire body motion, including both breast movement of respiration and posture changes in a bed. The experiment was carried out under regulated posture changes and under a sleeping condition by measuring heart rate, respiration and digitized image sequences using a video camera. A temporal increase in heart rate reflected the magnitude of physical activities. We proposed two candidate parameters for evaluation of respiratory and physical activities based on comparison among experimental results. The average of squared motion velocities reflected the magnitude of physical activities. The representative field-averaged component showed a waveform with periodic fluctuation corresponding to that of respiration obtained with a nasal thermistor.

A method for measuring respiration and physical activity in bed by optical flow analysis

A fully noncontact and unconstrained monitoring method, based on optical flow of movement of body surface that is developed by introducing image sequence analysis, is described. A spatiotemporal local optimization method is applied to determine optical flow in the image sequence. The optical flow visualizes the apparent velocity field of the entire body motion, including breast movement due to respiration and posture changes in a bed. A temporal increase in heart rate reflects the magnitude of physical activities. We propose two candidate parameters for evaluation of respiratory and physical activities based on comparison among experimental results. The average of squared motion velocities reflects the magnitude of physical activities. The representative field-averaged component shows a waveform with periodic fluctuation corresponding to that of respiration obtained with a nasal thermistor. This optical flow analysis is a promising new technique for evaluation of body motion for clinical use.

Oscillation and Synchronization in the Combustion of Candles

We investigate a simple experimental system using candles; stable combustion is seen when a single candle burns, while oscillatory combustion is seen when three candles burn together. If we consider a set of three candles as a component oscillator, two oscillators, that is, two sets of three candles, can couple with each other, resulting in both in-phase and antiphase synchronization depending on the distance between the two sets. The mathematical model indicates that the oscillatory combustion in a set of three candles is induced by a lack of oxygen around the burning point. Furthermore, we suggest that thermal radiation may be an essential factor of the synchronization.

Mechanism of Candle Flame Oscillation: Detection of Descending Flow above the Candle Flame

When several candles are bundled together, the size of the combined candle flame oscillates. We carried out observational experiments to understand the mechanism of this oscillation. These were optical imaging, shadow graph imaging, temperature imaging around the oscillating candle flame, and image analysis to obtain the quantitative velocity distribution of the air flow above the candle flame. The experiments detected the descending air flow to the candle flame from the upper area, and showed that the descending air flow is involved with the candle flame oscillation. According to the results, we propose a new mechanism of the candle flame oscillation using the analogy of the cumulonimbus cloud in meteorology.

Observation of Two-Dimensional Brownian Motion by Microscope Image Sequence Processing.

We propose a method to measure Brownian motion based on image sequence processing. Random motion of sub-micron sphere particles is visualized under an inverted microscope with laser light illumination. We analyze a long image sequence of the motion by a spatial-filtering method, which corresponds to dynamic light scattering. We confirm that bigger particle (diameter=1.09 µm) show ideal Brownian motion with an inverse power-law spectrum P ( f )∝ f -2 . In tiny particles (diameter=0.46 and 0.20 µm), however, we observe a deviation from f -2 behavior. When the motion of particles is limited within a two-dimensional plane by use of heavy water, ordinary behavior of f -2 spectrum is recovered. We confirm high reliability and big advantages of the proposed method compared to dynamic light scattering.

A speech-driven embodied group entrainment system with the model of lecturer's eyeball movement

We have already developed a speech-driven embodied group entrained communication system called “SAKURA” for activating group interaction and communication. In this system, a speech-driven computer graphics (CG) characters called InterActors with functions of both speaker and listener are entrained to one another as a teacher and some students in a virtual classroom by generating communicative actions and movements. In this study, for the basic research of realizing smooth communication during embodied interaction between human and robot, we analyzed the eyeball movements of a lecturer communicating in a virtual group by using an embodied communication system with a line-of-sight measurement device. On the basis of the analysis results, we propose an eyeball movement model that consists of a saccade model and a model of a lecturers gaze at an audience, called “group gaze model.” Then, we developed an advanced communication system in which the proposed model was used with SAKURA for enhancing group interaction and communication. This advanced system generates a lecturers eyeball movement on the basis of the proposed model by using only speech input. We used sensory evaluation in the experiments to determine the effects of the proposed model. The results showed that the system with the proposed model is effective in group interaction and communication.

Angle illusion in a straight road

We report a new angle illusion observed when viewing a real scene involving a straight road. The scene portrays two white lines which outline a traffic lane on a road and converge to a vanishing point. In experiment 1, observers estimated the angle created by these converging lines in this scene or in its image projected onto a screen. Results showed strong underestimation of the angle, ie over 50% for observations of both the real scene and its projected image. Experiment 2 assessed how depth cues in projected images influence the angle illusion. Results showed that this angle illusion disappeared when scene information surrounding convergent lines was removed. In addition, the illusion was attenuated with projection of an inverted scene image. These findings are interpreted in terms of a misadoption of depth information in the processing of angle perception in a flat image; in turn, this induces a massive angle illusion.

The Proposal of a Neuron Model in Consideration of Facilitation and Fatigue

In the past research on the neural transform model, some researchers took both excitation and inhibition factors into consideration. However, these past models relate to diffusion of the substance between neighboring cells, therefore these models are not rational for considering both excitation and inhibition factors in a separate cell. When repeated stimulation depolarizes a presynaptic axon terminal, the level of Ca2+ in the presynaptic axon terminal is increased. Thus, an increased number of quanta of transmitter are released. On the other hand, the release of the transmitter will result in the decrease in the quantity of the transmitter in the presynaptic axon terminal. Based on these physiology characteristics of synaptic transmission, we propose a new model in which facilitation and fatigue are both considered in a separate cell. Using the proposed model, short-term memory process, image feature detection and other image processing were simulated. We suggest that the proposed model is a valid and widely applicable neural model.

Eyeball Movement Model for Lecturer Character in Speech-Driven Embodied Group Entrainment System

In our previous research, we proposed an eyeball movement model that consists of a saccade model and a group gaze model for enhancing group interaction and communication. In this study, in order to evaluate the effects of the proposed model, we develop an advanced communication system in which the proposed model is used with a speech-driven embodied group entrained communication system. The effectiveness of the proposed model is demonstrated for performing the communication experiments with a sensory evaluation using the developed system.