An Experimental Study of Unsteady Flows Generated in Kojima Lake

The global positioning system (GPS) is utilized for analysis of flows in the water environment. A float equipped with a GPS unit is designed to drift on the surface of the water. Its driving force is the fluid resistance exerted on a pair of rectangular plates. While it travels over the surface, the GPS unit evaluates its position every second, and spatiotemporal data that specify its motion are transmitted to be recorded. Results of experiments conducted to study unsteady flows generated in Kojima Lake are introduced

Dynamics of a Cavitating Propeller in a Water Tunnel

This study investigates the unsteady dynamics and inherent instabilities of a cavitating propeller operating in a water tunnel. First, the steady characteristics of the cavitating propeller such as the thrust coefficient are obtained by applying continuity and momentum equations to a simple one-dimensional flow tube model. The effects of the tunnel walls as well as those of the propeller operating conditions (advance ratio and cavitation number) are explored. Then the transfer matrix of the cavitating propeller (considered to be the most appropriate way to describe the dynamics of propeller) is obtained by combining the simple stream tube model with the conventional cavity model using the quasi-static cavitation compliance and mass flow gain factor representation. Finally, the surge instability of a cavitating propeller observed by Duttweiler and Brennen (2001) is examined by coupling the present model of the cavitation with a dynamic model for the water tunnel. This analysis shows that the effect of tunnel walls is to promote the surge instability

Positional Order and Diffusion Processes in Particle Systems

Nonequilibrium behaviors of positional order are discussed based on diffusion processes in particle systems. With the cumulant expansion method up to the second order, we obtain a relation between the positional order parameter $\Psi$ and the mean square displacement $M$ to be $\Psi \sim \exp(- {\bf K}^2 M /2d)$ with a reciprocal vector ${\bf K}$ and the dimension of the system $d$. On the basis of the relation, the behavior of positional order is predicted to be $\Psi \sim \exp(-{\bf K}^2Dt)$ when the system involves normal diffusion with a diffusion constant $D$. We also find that a diffusion process with swapping positions of particles contributes to higher orders of the cumulants. The swapping diffusion allows particle to diffuse without destroying the positional order while the normal diffusion destroys it.Comment: 4 pages, 4 figures. Submitted to Phys. Rev.

ATTITUDES TOWARDS CATCHING AND KILLING THE YAMABIRU (LAND LEECH) IN THE TENRYU AREA, JAPAN

Recently, yamabiru, or land leeches (Haemadipsa zeylanica japonica), have proliferated in prefectures across Japan. Since it is unlikely that they will disappear from the living spaces, fields, and forests in which humans live and work, people living in the new contact zones have devised methods to coexist with them. The field research was conducted in 2017 and 2018 in C Township in the Tenryu area. Like many rural areas in Japan, C Township is facing the challenges of depopulation and ageing, and is home to a group of residents who aim for local revitalization. The participatory observation of leech-catching, an activity practiced by the group members who dare to use their hands to kill yamabiru instead of chemicals, provides several implications regarding ethical attitudes and the role of the human body. This paper argues that the members do not behave as victims suffering from the damage caused by yamabiru and do not kill them out of anger or discomfort. Instead, by behaving as an assailant and seeking out the concrete feeling of killing by direct contact, the members attempt to control their disastrous impact on other creatures and the environment. This behavior invites us to pay closer attention to the role of the human body and of bodily interaction as a sensory tool to coexist with other creatures in the Anthropocene, an era full of risks and uncertainty

LIFE WITH THE YAMABIRU (LAND-DWELLING LEECH) AFTER THE FAILURE OF A FENCE IN RURAL JAPAN

In recent years, Haemadipsa zeylanica japonica, a land-dwelling leech referred to as a “yamabiru” in Japanese, has proliferated in the countryside of Japan, because wild animals are a vector of the yamabiru. In some areas, the yamabiru suck the blood of people even in houses. This paper explores how residents living in a yamabiru “hot spot,” where the number of yamabiru is large, have coexisted with the creature which, though troublesome, is almost impossible to avoid. Z City in Kanagawa Prefecture attempted to maintain a long fence to prevent wild animals from entering the “human domain,” although this did not work as expected. Instead, the daily contact between people and the yamabiru generated various relationships other than a simple, hostile relationship: kill-or-be-killed. The trouble caused by the yamabiru encourages the interviewees to rethink their society and history, though coexistence with the yamabiru can never do away with the dream of extermination. Coexistence with yamabiru, in this context, means not living separately, but living with trouble in the contact zone, without making clear-cut borders between human and non-human domains. This paper attempts to demonstrate that people can make efforts to create various relationships even with “real,” not metaphorical, parasites. Insights from this research may bring to light new information that will be of value to contemporary society, where numerous borders that divide people and social groups are being drawn