Dosimetry in Japanese male and female models for a low-frequency electric field

The present study quantified induced current in anatomically based Japanese male and female models for exposure to low-frequency electric fields. A quasi-static finite-difference time-domain (FDTD) method was applied to analyze this problem. For our computational results, the difference of the induced current density averaged over an area of 1 cm2 between Japanese male and female models was less than 30% for each nerve tissue. The difference of induced current density between the present study and earlier works was less than 50% for the same conductivities, despite the different morphology. Particularly, maximum current density in central nerve tissues appeared in the retina of Japanese models, the same as in the earlier works.journal articl

Modeling time variation of blood temperature in a bioheat equation and its application to temperature analysis due to RF exposure

The present study discusses a scheme to take into account core temperature variation in a well-known bioheat equation. First, the limitation in conventional modeling of the bioheat equation was investigated for a problem in which the whole-body phantom should be taken into account. Then, schemes for varying body-core temperature in the bioheat equation were discussed for radio-frequency exposures. The computational uncertainty in the core temperature elevation was found to be reasonable when a proper scheme for computing the net rate of heat acquisition by blood from body tissue was introduced.application/pdfjournal articl

Significant Gas-to-Dust Ratio Asymmetry and Variation in the Disk of HD 142527 and the Indication of Gas Depletion

We investigate the dust and gas distribution in the disk around HD 142527 based on ALMA observations of dust continuum, 13CO(3-2), and C18O(3-2) emission. The disk shows strong azimuthal asymmetry in the dust continuum emission, while gas emission is more symmetric. In this paper, we investigate how gas and dust are distributed in the dust-bright northern part of the disk and in the dust-faint southern part. We construct two axisymmetric disk models. One reproduces the radial profiles of the continuum and the velocity moments 0 and 1 of CO lines in the north and the other reproduces those in the south. We have found that the dust is concentrated in a narrow ring having ~50AU width (in FWHM; w_d=30AU in our parameter definition) located at ~170-200AU from the central star. The dust particles are strongly concentrated in the north. We have found that the dust surface density contrast between the north and south amounts to ~70. Compared to the dust, the gas distribution is more extended in the radial direction. We find that the gas component extends at least from ~100AU to ~250AU from the central star, and there should also be tenuous gas remaining inside and outside of these radii. The azimuthal asymmetry of gas distribution is much smaller than dust. The gas surface density differs only by a factor of ~3-10 between the north and south. Hence, gas-to-dust ratio strongly depends on the location of the disk: ~30 at the location of the peak of dust distribution in the south and ~3 at the location of the peak of dust distribution in the north. Despite large uncertainties, the overall gas-to-dust ratio is inferred to be ~10-30, indicating that the gas depletion may have already been under way.Comment: 39 pages, 37 figures, 9 tables, accepted for publication in PAS

The correlation between mass-averaged SAR and temperature elevation in the human head model exposed to RF near-fields from 1 to 6 GHz.

In the present study, we investigate the relationship between the mass-averaged specific absorption rate (SAR) and temperature elevation in anatomically based Japanese head models due to the dipole antenna. A homogeneous cubical model is also used as a basis for the investigation. The frequency region considered is from 1 to 6 GHz. We focused on the averaging mass of SAR, which maximizes the correlation with local temperature elevation. An averaged SAR over 10 g was found to reasonably correlate with local temperature elevation even for frequencies from 3 to 6 GHz. The dominant factor influencing the correlation between mass-averaged SAR and temperature elevation is suggested to be the thermal diffusion length in biological tissue, together with the penetration depth of radio-frequency waves. The correlation of local temperature elevation to mass-averaged SAR is largely influenced by the blood perfusion rate, while at most 10% or less is due to the pinna, model inhomogeneity and the antenna position relative to the head model.application/pdfjournal articl

Influence of electromagnetic polarization on the whole-body averaged SAR in children for plane-wave exposures

The present study investigated the whole-body averaged specific absorption rate (WBSAR) in an infant model with the finite-difference time-domain method. The focus of the present study is the effect of polarization of incident electromagnetic waves on the WBSAR. This is because most previous studies investigated the WBSAR for plane-wave exposure with a vertically aligned electric field. Our computational results revealed that the WBSAR for plane-wave exposure with a vertically aligned electric field is smaller than that with a horizontally aligned electric field for frequencies above 2 GHz. The main reason for this difference is attributed to be the component of the surface area perpendicular to the electric field of the incident wave.application/pdfjournal articl

Dynamic travel demand models incorporating un observed heterogeneity and First-order serial correlation 【Article】

Very little work using repeated cross-sectional data has been undertaken in transport research. This is especiallytrue for travel data gathered at multiple points in time, especially data that is gathered every 5-10 years such asUrban Area Travel Survey Data and Road Traffic Census Data in Japan. Accordingly, travel demand modelingbased on these types of data is not yet fully developed. This paper deals with methods for developing models whichinclude time series factors for predicting travel demand using three time-points travel data gathered in Hiroshima.As a result, it was shown that model parameters based on cross-sectional data were not stable over time by usingCovariance Analysis or T-Statistic. The existence of first-order serial correlation in residuals was confirmed byusing Generalized Durbin-Watson Statistics, while unobserved heterogeneity was checked by using Breusch-PaganStatistics. Fixed-effects models using these two factors were developed and it was shown that their predicting accu-racy was improved in comparison to traditional cross-sectional models

FDTD analysis of human body-core temperature elevation due to RF far-field energy prescribed in the ICNIRP guidelines

This study investigated the relationship between the specific absorption rate and temperature elevation in an anatomically-based model named NORMAN for exposure to radio-frequency far fields in the ICNIRP guidelines (1998 Health Phys. 74 494?522). The finite-difference time-domain method is used for analyzing the electromagnetic absorption and temperature elevation in NORMAN. In order to consider the variability of human thermoregulation, parameters for sweating are derived and incorporated into a conventional sweating formula. First, we investigated the effect of blood temperature variation modeling on body-core temperature. The computational results show that the modeling of blood temperature variation was the dominant factor influencing the body-core temperature. This is because the temperature in the inner tissues is elevated via the circulation of blood whose temperature was elevated due to EM absorption. Even at different frequencies, the body-core temperature elevation at an identical whole-body average specific absorption rate (SAR) was almost the same, suggesting the effectiveness of the whole-body average SAR as a measure in the ICNIRP guidelines. Next, we discussed the effect of sweating on the temperature elevation and thermal time constant of blood. The variability of temperature elevation caused by the sweating rate was found to be 30%. The blood temperature elevation at the basic restriction in the ICNIRP guidelines of 0.4 W kg?1 is 0.25 °C even for a low sweating rate. The thermal time constant of blood temperature elevation was 23 min and 52 min for a man with a lower and a higher sweating rate, respectively, which is longer than the average time of the SAR in the ICNIRP guidelines. Thus, the whole-body average SAR required for blood temperature elevation of 1 °C was 4.5 W kg?1 in the model of a human with the lower sweating coefficients for 60 min exposure. From a comparison of this value with the basic restriction in the ICNIRP guidelines of 0.4 W kg?1, the safety factor was 11.application/pdfjournal articl