In this paper, using the time-continuous model of short-term memory, we have studied the optimum-apportionment modes of the presentation time of seven randomly-selected alphabet letters sequentially presented in the same position on a CRT display unit screen visually and through a headphone acoustically to four young males. These modes are thought to allow for the easiest retention by the short-term memory. The average optimum-apportionment mode, as an average of individual scores of the optimum-apportionment mode, was also obtained. These modes have shown the same tendency as those in a visual display or in an auditory display. That is, the presentation time of the alphabet letters presented in the first part is long and the presentation time of the alphabet letters presented in the latter part is short. Individual differences appear in the middle part. There are two cases in this part of the optimum-apportionment mode: in the first case, the presentation time of one alphabet letter is longer than that of previous alphabet letter and the following alphabet letter. In the other case, the presentation time of the alphabet letters decreases monotonically according to its serial position. However, the minimum presentation time is 100ms shorter than that in the auditory display. The number of recalled alphabet letters with the optimum-apportionment mode is larger than that in the visual display or in the auditory display for all subjects.

View full abstract

The human brain wave induced by flickering lights (Visual Evoked Potential: VEP) was investigated for the possible application to a special GUI system. The flickering frequency of 8-12Hz was found to elicit large VEP amplitudes when the stimulating LED was being gazed at. Shifting the fixation point reduced the VEP amplitude, e. g., about 50% reduction by 2.5 degree shift. The study was extended for the situation of multiple LED sources. When the flickering frequencies were all different in the range of 8-12Hz, the VEP frequency component corresponding to the fixation LED produced the largest amplitude. When the frequencies were the same but there were phase (timing) differences, it was also possible to tell, by the VEP phase comparison, which LED was being gazed at. These results seem to suggest the feasibility of using VEP for the handicapped to select GUI icons displayed on a CRT monitor.

View full abstract

The prototype system of a chirp radar-type microwave computed tomography whose data acquisition time is approximately 100 minutes has been developed for non-invasive thermometry of the human body. The roughly estimated spatial resolution is 1cm and 0.7°C temperature difference is visualized two dimensionally. Since the diffracted or reflected waves can automatically be removed from projection data by the hardware-based signal processing, the tomogram is reconstructed easily by applying a simple algorithm employed in an X-ray CT. However, techniques for high-speed imaging must be developed for practical application of the tomography system. In the paper, techniques to reduce the data acquisition time have been discussed. It is evident that quick sweep of the chirp pulse signal, data acquisition in time-domain, electronic scan of antennas can reduce the data acquisition time. By using an array antenna system, measurement can be done at many points simultaneously. By adopting those techniques, it could be shortened to approximately one fortieth or more than the prototype system.

View full abstract

To design comfortable clothing, a quantitative assessment of clothing comfort is important. However, no effective assessment methods have been developed. In this study we carried out wearing tests and evaluated clothing comfort quantitatively using a three-layered neural network (NN) by back-propagating errors. In the wearing tests, cotton, polyester, and modified polyester apparel were used. Three subjects were kept at rest during 120 minutes' exposure to three consecutive ambient humidity changes (40→75→40%) at 33.0°C. Skin temperatures at 6 sites on the body, temperature and humidity inside the clothing, weight loss, and wearing sensation were measured. In the NN, the number of input factors was considered in two different cases; one with 9 physical factors, and the other with 12 factors adding three subjective factors. Clothing comfort was used as an output of the NN. An increase in the generalizing ability of the NN was observed when the subjective factors were added. Similar results were obtained using quadratic-multivariate analysis with twelve input factors and it was confirmed that the sensations in clothing were important factors when evaluating clothing comfort. A difference between hydrophilic and hydrophobic fibers was observed as follows as a difference in generalizing ability and weight coefficients in this model and the effects of clothing material on clothing comfort was made evident. The generalizing ability of clothing comfort in cotton clothing was smaller than that in polyester clothing and modified polyester had similar weight coefficients of the networks to cotton in the learning of the NN, both ascribable to the fact that water sorption ability in cotton and modified polyester was larger than that in polyester. It was also found that evaluation by NN was very useful for even an object which was difficult to model exactly, such as in an experiment with physiological changes.

View full abstract

Fluorescent X-ray induced by monochromatic synchrotron X-ray is quite useful to describe the distribution of non-radioactive target materials in the body with high sensitivity. The target material emits characteristic fluorescent X-ray by the excitation. From the detected fluorescence, we can estimate the amount of target material in the crossing volume between excitation beam and observed area. Thus, by scanning both excitation beam and observation area, we can reconstruct the tomographic image of target material distribution. To estimate the amount of target material, we must detect both excitation and fluorescent X-ray intensity with proper correction for their attenuation in the object. However, the structure of the object itself is just under examination. Here an algorithm is developed to correct the absorption of incident X-ray and induced fluorescence respectively along the optical path in the object. From observed spectrum, we can discriminate target material and tissue, then the characteristic of observed volume area in the object is estimated, and the absorption corrections and exact estimations are done sequentially along scanning sequence. An experimental scanning fluorescent X-ray tomography system with monochromatic SR X-ray is constructed. Reconstructed images for phantom with iodine demonstrate usefulness of above procedure. The minimum detectable density of target material was 50μg/ml in this experiment. Here quantization procedure for spectrum measurement is also prepared and the linear relationship between the fluorescent intensity and the amount of target material is confirmed experimentally. Finally, further improvements to realize practical system are discussed on detecting system, reconstruction algorithm, etc. and optimum energy spectrum of incident X-ray.

View full abstract

In this paper, the relation between input rate of alphabet letters into short-term memory and its retention efficiency is investigated based upon time-continuous model of short-term memory. This model study reveals that retention efficiency is high in the vicinity of 10ms as well as 300ms for input time per letter.

View full abstract