This study evaluated the signal transmission characteristics, the electromagnetic field distributions in and around the human body, and the biosafety criteria of magnetically coupled intra-body communication through computer simulation. The analyzed magnetic couplings were a normal inductive coupling (non-resonant coupling) and two types of resonant couplings. The target evaluation regions were the forearm and upper body, and we analyzed up to an inter-coil distance of 100 cm, which is considered to be the assumed human body communication range. The results of the frequency characteristics of the signal path loss, which were the same as before, revealed that the amount of signal loss for the inductive coupling was minimized between 2 and 3 MHz at each coil distance; one of the resonant couplings could improve the signal path loss by approximately 20 dB at a resonant frequency of 2 MHz. Furthermore, when the signal voltage was 1 V, the electric field strength in the body was smaller than the general environmental limit value by more than two orders of magnitude. The local specific absorption rate was smaller by approximately four orders of magnitude; thus, it was concluded that the magnetic field method is very safe for the living body.

In the determination of radioactivity in samples such as soil and water, a simple method with acceptable accuracy is desirable. A simulation is used for verifying the method under various conditions. The conventional sum-peak method and the modified sum-peak method were developed as simple absolute measurement techniques. However, it is known that radioactivity is underestimated in volume source samples, which concerns to the angular correlation of two gamma rays, the geometric effect, and the self-absorption in the sample. These effects depend on the Source-to-Detector-Distance (SDD) and the influences are difficult to measure separately. In this paper, we investigated the dependence of calculated radioactivity on SDD by using the Geant4 Monte Carlo simulation. The simulation modeled a high purity Germanium detector system and a volume source. The results showed that the effect of angular correlation and the geometric effect is significant when the SDD is less than 10 cm, whilst the self-absorption is the main factor of the underestimation and the constant when the SDD is larger than 10 cm.

To explain that left-right symmetric and asymmetric size (mass) ratios observed in biological particle-pairs of molecules and cells in nature and child atoms of nuclear fission, the stochastic differential equation model of three-dimensional momentum conservation law and weakest stability principle (quasi-stability theory) is proposed by Naitoh (J. of Physics, 2012). The three-dimensional momentum conservation law considers vector quantity (i.e. velocity), while conventional theories started from Bohr have been based on energy conservation law. Naitoh qualitatively showed a possibility of bi-modal distribution of mass and size based on one-dimensional Taylor expansion. Furthermore, we have shown that the size and mass ratios of those particles are predicted more accurately by using multi-dimensional Taylor expansion in the previous report (Kobayashi and Naitoh, JASSE, 2019). Moreover, classification of dynamical terms in the stochastic model into three groups has revealed that the input energy level of neutron provided for nuclear fission varies the frequency distribution plotted against child atom mass generated. In this report, we clarify the mass-frequency distribution of atoms generated in cold fusion phenomenon, by using the stochastic differential equation model. After the multi-dimensional Taylor expansion is applied to the stochastic differential equation model of three-dimensional momentum conservation law, the stability theory qualitatively reveals the mass frequency distribution of child atoms generated in the cold fusion experiment (A. B. Karabut, JCMNS, 2012).

To promote evacuation at disaster occurrence, appropriate local information needs to be certainly transmitted to evacuees. However, in a city disaster case, the people who are not living in and just visit the city, for instance as tourists, might have little knowledge on the local evacuation information. In such cases, disaster prevention administrative radio systems, that are operated as one of the information transmission systems at present, are useful to transmit wide-area disaster information, but inappropriate for transmitting adaptive localized evacuation information. Therefore, we propose a narrow-area specific messaging system using taxis as information transmitters. As the experimental results, it is found that decentralized and unbiased taxi allocation can accelerate evacuation completion. Moreover, we propose a method to select evacuation sites by using the elapsed time after the disaster occurrence and the hazard map information. The proposed method is compared with the shortest-path finding method of the evacuation sites by computer simulations. Consequently, it is found that when the evacuation behavior is delayed, the proposed method outperforms the shortest-path finding method by about 5%.

Tritiated water is generated under the decommissioning process of the Fukushima Daiichi Nuclear Power Station. The Ministry of Economy, Trade and Industry, Japan (METI) and Tokyo Electric Power Company Holdings (TEPCO) are considering releasing tritium into the ocean. In addition, tritium is planning to use as fuel in fusion power plants, which is expected as a future power generation technology. Therefore, it is important to understand the impact of tritium on biomolecules in living organisms including human in detail. We aim to elucidate the mechanism of DNA damage due to the radioactive decay effect that occurs when light hydrogen in human DNA is replaced with tritium, using molecular dynamics (MD) methods. To understand the decay effect on DNA, first, it is necessary to evaluate the replaceability of light hydrogen to tritium for each hydrogen in DNA. In this study, to evaluate the degree of replaceability of the backbone hydrogen atoms in telomeric DNA of human, solvent-accessible surface area (SASA) is calculated for the data obtained by MD simulation. As a result, it is found that the SASA of H5 hydrogen is large in the hydrogen atoms in the backbone.

Various traffic simulation models have been proposed according to the phenomena of interest, the required reproducibility, and the size of the target area. One of them is a hybrid traffic simulation approach that employs two or more models with different granularity depending on the traffic conditions and the properties of road networks. Among them, a dynamic hybrid traffic simulation, which dynamically switches the application area of each model during the simulation running, seems to have the potential to be applied to a wide area while keeping high reproducibility. However, because there are few studies on this subject, the decision criteria for model switching and its effects have not been sufficiently investigated. In this study, the authors proposed a novel dynamic hybrid traffic simulation method, especially a model switching criterion, and evaluated its performance. In addition, the proposed model is validated using data obtained from real highways. The results show that the proposed model is applicable for highway simulations with high accuracy and low computational cost.