arXiv subjects

Yu Ohki

Publications and source records attributed to Yu Ohki.

4 recordsLinked to original sources

arXiv2025

Visualization of Interpersonal Communication using Indoor Positioning Technology with UWB Tags

In conjunction with a social gathering held on a university campus, the movement of attendees were tracked within the venue for approximately two hours using a UWB indoor positioning system, in order to visualize their interpersonal communication. Network and community analyses were performed on attendee interaction data, and the evolution of communities over time was further investigated through repeated community analysis at different time points. Furthermore, recognizing the influence of distance thresholds on defining contact, we discussed how varying these thresholds affected the resulting network structure and community analysis outcomes. This study confirmed that the temporal evolution of communities identified through community analysis broadly corresponded with the visually observed groupings of participants using the UWB indoor positioning system.

cs.SI↗

arXiv2022

First Demonstration Experiment for Energy Trading System EDISON-X Using the XRP Ledger

We develop an energy trading system, EDISON-X, that uses blockchain technology to manage the buying and selling of electricity usage rights, i.e., tokens. UPX and SPX tokens purchase electricity from the utility company's distribution lines and the photovoltaic panels. On July 1, 17 students in our school dormitory participated in an experiment to confirm the operation of the EDISON-X system. Based on the results of this experiment, we discuss the energy trading system using blockchain technology for the effective usage of renewable energy. We develop topology and network science methodologies to understand the characteristics of energy trading. We test the hypothesis that market transactions become less active when ``cavities'' appear using persistent homology. The preliminary result implies that the hypothesis could be adopted. We, however, need more data samples.

cs.CR↗

arXiv2022

Regional medical inter-institutional cooperation in medical provider network constructed using patient claims data from Japan

The aging world population requires a sustainable and high-quality healthcare system. To examine the efficiency of medical cooperation, medical provider and physician networks were constructed using patient claims data. Previous studies have shown that these networks contain information on medical cooperation. However, the usage patterns of multiple medical providers in a series of medical services have not been considered. In addition, these studies used only general network features to represent medical cooperation, but their expressive ability was low. To overcome these limitations, we analyzed the medical provider network to examine its overall contribution to the quality of healthcare provided by cooperation between medical providers in a series of medical services. This study focused on: i) the method of feature extraction from the network, ii) incorporation of the usage pattern of medical providers, and iii) expressive ability of the statistical model. Femoral neck fractures were selected as the target disease. To build the medical provider networks, we analyzed the patient claims data from a single prefecture in Japan between January 1, 2014 and December 31, 2019. We considered four types of models: a model using node strength and linear regression to a model using feature representation by node2vec and regression tree ensemble, which is a machine learning method. The results showed that a stronger medical provider reduces the duration of hospital stay. The overall contribution of the medical cooperation to the duration of hospital stay extracted from the medical provider network using node2vec is approximately 20%, which is approximately 20 times higher than the model using strength.

physics.soc-ph↗

arXiv2021

Community Structure and Its Stability on a Face-to-Face Interaction Network in Kyoto City

As social behavior plays an essential role in people's lives, the features of face-to-face interaction networks must be examined to understand people's social behavior. In this study, we focused on the stable community structure of a face-to-face interaction network because it explains the persistent communities caused by the stationary communication patterns of citizens and visitors in a city. We regarded citizens and visitors as two kinds of particles and the community as a phase and theorized the stability of the community structure using the equilibrium conditions among communities. We formulated the chemical potentials of the communities and examined whether they were in equilibrium under the assumption of a canonical ensemble. We estimated the chemical potentials of persistent communities and found that these values matched within approximately 10% error for each day. This result indicates that the cause of persistent communities is the stability of community structure.

physics.soc-ph↗