Osamu Fujiwara

Bio: Osamu Fujiwara is an academic researcher from Nagoya Institute of Technology. The author has contributed to research in topics: Electrostatic discharge & Electromagnetic field. The author has an hindex of 32, co-authored 303 publications receiving 3563 citations.

FDTD computation of temperature rise in the human head for portable telephones

Abstract: Temperature rises in the human head for portable telephones were computed with an anatomically based head model at 900 MHz and 1.5 GHz. The specific absorption rate (SAR) in the human head was determined using the finite-difference time-domain (FDTD) method, while a bioheat equation was numerically solved also using the FDTD method. The portable telephone was modeled by a quarter-wavelength monopole antenna on a dielectric covered metal box. The source geometries considered were the telephone barely touching the ear and the telephone pressing the ear, both having a vertical alignment at the side of the head. The antenna output power was set to be consistent with the portable telephones of today: 0.6 W at 900 MHz and 0.27 W at 1.5 GHz. Computed results show that a phone time of 6-7 min yields a temperature rise of approximately 90% of the steady-state value. Application of the ANSZ/IEEE safety guidelines restricting the 1-g-averaged spatial peak SAR to 1.6 W/kg results in the maximum temperature rise in the brain of 0.06/spl deg/C, and application of the ICNIRP/Japan safety guidelines restricting the 10-g-averaged spatial peak SAR to 2 W/kg results in the maximum temperature rise in the brain of 0.11/spl deg/C, both at 900 MHz and 1.5 GHz.

Comparisons of computed mobile phone induced SAR in the SAM phantom to that in anatomically correct models of the human head

Abstract: The specific absorption rates (SAR) determined computationally in the specific anthropomorphic mannequin (SAM) and anatomically correct models of the human head when exposed to a mobile phone model are compared as part of a study organized by IEEE Standards Coordinating Committee 34, Sub-Committee 2, and Working Group 2, and carried out by an international task force comprising 14 government, academic, and industrial research institutions. The detailed study protocol defined the computational head and mobile phone models. The participants used different finite-difference time-domain software and independently positioned the mobile phone and head models in accordance with the protocol. The results show that when the pinna SAR is calculated separately from the head SAR, SAM produced a higher SAR in the head than the anatomically correct head models. Also the larger (adult) head produced a statistically significant higher peak SAR for both the 1- and 10-g averages than did the smaller (child) head for all conditions of frequency and position.

Characteristics of the SAR distributions in a head exposed to electromagnetic fields radiated by a hand-held portable radio

Abstract: Presents characteristics of the specific absorption rate (SAR) distributions calculated by the finite-difference time-domain (FDTD) method using a heterogeneous and realistic head model and a realistic hand-held portable radio model. The difference between the SAR distributions produced by a 1/4-wavelength monopole antenna and those produced by a 1/2-wavelength dipole antenna is investigated. The dependence of the maximum local SAR on the distance d/sub a/ between the auricle of the head and the antenna of the radio is evaluated. It is shown that the maximum local SAR decreases as the antenna length extends from 1/4 to 1/2 of the wavelength. The maximum local SAR's in a head model with auricles are larger than these in one without auricles. The dependence of the SAR on the electrical inhomogeneity of the tissues in the head model is not significant with regard to the surface distribution and the maximum local SAR when the radio is near the head. It is also shown that the maximum local SAR is not strongly dependent on the position of the hand when the hand does not shade the antenna. Furthermore, the SAR's experimentally measured in a homogeneous head phantom are compared with the calculated SAR's.

Comparison and evaluation of electromagnetic absorption characteristics in realistic human head models of adult and children for 900-MHz mobile telephones

Abstract: The controversy on the dosimetry in children's heads for mobile telephones is still inconsistent Gandhi's group [1996, 2002] reported a considerable increase of the spatial peak specific absorption rate (SAR) in children's heads, while Kuster's group [1998] claimed that there was not a significant difference in the SAR between children and adults In this paper, based on Japanese children's statistical data on external shapes of heads, we developed two kinds of children's models from a Japanese adult head model Using the children's head models, we calculated the local peak SAR under the same conditions as those previously employed by Gandhi's and Kuster's groups Compared to the local peak SAR in the adult head model, we found a considerable increase in the children's heads when we fixed the output power of the monopole-type antenna, but no significant differences when we fixed the effective current of the dipole-type antenna This finding suggests that the contradictory conclusions drawn by the above two groups may be due to the different conditions in their numerical peak SAR calculations

FDTD calculation of whole-body average SAR in adult and child models for frequencies from 30 MHz to 3 GHz.

Abstract: Due to the difficulty of the specific absorption rate (SAR) measurement in an actual human body for electromagnetic radio-frequency (RF) exposure, in various compliance assessment procedures the incident electric field or power density is being used as a reference level, which should never yield a larger whole-body average SAR than the basic safety limit. The relationship between the reference level and the whole-body average SAR, however, was established mainly based on numerical calculations for highly simplified human modelling dozens of years ago. Its validity is being questioned by the latest calculation results. In verifying the validity of the reference level with respect to the basic SAR limit for RF exposure, it is essential to have a high accuracy of human modelling and numerical code. In this study, we made a detailed error analysis in the whole-body average SAR calculation for the finite-difference time-domain (FDTD) method in conjunction with the perfectly matched layer (PML) absorbing boundaries. We derived a basic rule for the PML employment based on a dielectric sphere and the Mie theory solution. We then attempted to clarify to what extent the whole-body average SAR may reach using an anatomically based Japanese adult model and a scaled child model. The results show that the whole-body average SAR under the ICNIRP reference level exceeds the basic safety limit nearly 30% for the child model both in the resonance frequency and 2 GHz band.

Principles of Neural Science

Abstract: I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Vocal affect expression: a review and a model for future research

Abstract: In reviewing the literature on the vocal expression of emotion, a discrepancy between reported high accuracy in vocal-auditory recognition and the lack of clear evidence for the acoustic differentiation of vocal expression is noted. The latter is explained by (a) a paucity of research on voice quality, (b) neglect of the social signaling functions of affect vocalization, and (c) insufficiently precise conceptualization of the underlying emotional states. A "component patterning" model of vocal affect expression is proposed that attempts to rink the outcomes of antecedent event evaluation to biologically based response patterns. On the basis of a literature survey of acoustic-phonetic evidence, the likely phonatory and articulatory correlates of the physiological responses characterizing different emotional states are described in the form of three major voice types (narrow-wide, lax-tense, full-thin). Specific predictions are made as to the changes in acoustic parameters resulting from changing voice types. These predictions are compared with the pattern of empirical findings yielded by a comprehensive survey of the literature on vocal cues in emotional expression. Although the comparison is largely limited to the tense-lax voice type (because acoustic parameters relevant to the other voice types have not yet been systematically studied), a high degree of convergence is revealed. It is suggested that the model may help to stimulate hypothesis-guided research as well as provide a framework for the development of appropriate research paradigms.

Communication of emotions in vocal expression and music performance: different channels, same code?

Abstract: Many authors have speculated about a close relationship between vocal expression of emotions and musical expression of emotions. but evidence bearing on this relationship has unfortunately been lacking. This review of 104 studies of vocal expression and 41 studies of music performance reveals similarities between the 2 channels concerning (a) the accuracy with which discrete emotions were communicated to listeners and (b) the emotion-specific patterns of acoustic cues used to communicate each emotion. The patterns are generally consistent with K. R. Scherer's (1986) theoretical predictions. The results can explain why music is perceived as expressive of emotion, and they are consistent with an evolutionary perspective on vocal expression of emotions. Discussion focuses on theoretical accounts and directions for future research.