Network Dynamics in the 12 Regional Clusters (Japanese)

It has been observed that the origination of innovation tends to concentrate in areas in which environmental conditions are formed as clusters. It is networks with "small-world" architecture that underpin the high level of creative power for innovation that clusters possess. If it were possible, through policy efforts, to form networks of a highly small-world character that provide an environment that can facilitate a good balance between short-distance interaction and long-distance interaction, that would lead to the enhancement of a region's creative power for innovation. The cluster policy currently being implemented has completed its first phase and has reached a watershed at which it moves into the second phase. In this paper we attempt to formulate a method of objectively grasping and evaluating network architecture from the standpoint of these two types of interaction. Specifically, with regard to the architecture of major networks formed domestically, we use network analysis methods to conduct a comparative analysis of the 12 regions and fields before (in 2000) and after (in 2005) the implementation of cluster policy. As a result of this, we have clarified the following points. (1) Networks are expanding in all regions, (2) the networks that excel in long-distance interaction also excel in short-distance interaction, (3) with a small number of exceptions, the bigger the network is, the more both of these characteristics are enhanced, (4) during this five-year period there have been no major changes with regard to the comparative advantage of each region or field, (5) there is some degree of correlation between the independence of modules and the extent of their small-world character, and (6) disparities between regions are greater than disparities between industry sectors. Through the use of this analytical method it was possible to obtain a quantitative grasp of network architecture in a form that made possible comparisons with other regions and fields, and from this to extract objective information necessary for policy-making. We hope that efficient networking activity will be carried out in the future on the basis of the results of analysis of this kind.

CO Multi-line Imaging of Nearby Galaxies (COMING). III. Dynamical effect on molecular gas density and star formation in the barred spiral galaxy NGC 4303

We present the results of $^{12}$CO($J$=1-0) and $^{13}$CO($J$=1-0) simultaneous mappings toward the nearby barred spiral galaxy NGC 4303 as a part of the CO Multi-line Imaging of Nearby Galaxies (COMING) project. Barred spiral galaxies often show lower star-formation efficiency (SFE) in their bar region compared to the spiral arms. In this paper, we examine the relation between the SFEs and the volume densities of molecular gas $n(\rm{H}_2)$ in the eight different regions within the galactic disk with CO data combined with archival far-ultraviolet and 24 $\mu$m data. We confirmed that SFE in the bar region is lower by 39% than that in the spiral arms. Moreover, velocity-alignment stacking analysis was performed for the spectra in the individual regions. The integrated intensity ratios of $^{12}$CO to $^{13}$CO ($R_{12/13}$) range from 10 to 17 as the results of stacking. Fixing a kinetic temperature of molecular gas, $n(\rm{H}_2)$ was derived from $R_{12/13}$ via non-local thermodynamic equilibrium (non-LTE) analysis. The density $n(\rm{H}_2)$ in the bar is lower by 31-37% than that in the arms and there is a rather tight positive correlation between SFEs and $n(\rm{H}_2)$, with a correlation coefficient of $\sim 0.8$. Furthermore, we found a dependence of $n(\rm{H}_2)$ on the velocity dispersion of inter-molecular clouds ($\Delta V/ \sin i$). Specifically, $n(\rm{H}_2)$ increases as $\Delta V/ \sin i$ increases when $\Delta V/ \sin i < 100$ km s$^{-1}$. On the other hand, $n(\rm{H}_2)$ decreases as $\Delta V/ \sin i$ increases when $\Delta V/ \sin i > 100$ km s$^{-1}$. These relations indicate that the variations of SFE could be caused by the volume densities of molecular gas, and the volume densities could be governed by the dynamical influence such as cloud-cloud collisions, shear and enhanced inner-cloud turbulence.Comment: 15 pages, 8 figures, accepted for publication in PAS

CO Multi-line Imaging of Nearby Galaxies (COMING) IV. Overview of the Project

Observations of the molecular gas in galaxies are vital to understanding the evolution and star-forming histories of galaxies. However, galaxies with molecular gas maps of their whole discs having sufficient resolution to distinguish galactic structures are severely lacking. Millimeter wavelength studies at a high angular resolution across multiple lines and transitions are particularly needed, severely limiting our ability to infer the universal properties of molecular gas in galaxies. Hence, we conducted a legacy project with the 45 m telescope of the Nobeyama Radio Observatory, called the CO Multi-line Imaging of Nearby Galaxies (COMING), which simultaneously observed 147 galaxies with high far-infrared flux in $^{12}$CO, $^{13}$CO, and C$^{18}$O $J=1-0$ lines. The total molecular gas mass was derived using the standard CO-to-H$_2$ conversion factor and found to be positively correlated with the total stellar mass derived from the WISE $3.4 \mu$m band data. The fraction of the total molecular gas mass to the total stellar mass in galaxies does not depend on their Hubble types nor the existence of a galactic bar, although when galaxies in individual morphological types are investigated separately, the fraction seems to decrease with the total stellar mass in early-type galaxies and vice versa in late-type galaxies. No differences in the distribution of the total molecular gas mass, stellar mass, and the total molecular gas to stellar mass ratio was observed between barred and non-barred galaxies, which is likely the result of our sample selection criteria, in that we prioritized observing FIR bright (and thus molecular gas-rich) galaxies.Comment: Accepted for publication in PASJ; 47 pages, 5 tables, 29 figures. On-line supplementary images are available at this URL (https://astro3.sci.hokudai.ac.jp/~radio/coming/publications/). CO data is available at the Japanese Virtual Observatory (JVO) website (https://jvo.nao.ac.jp/portal/nobeyama/coming.do) and the project website (https://astro3.sci.hokudai.ac.jp/~radio/coming/data/

Different Precipitation Systems between Hiroshima and Keihanshin during Extreme Rainfall Event in Western Japan in July 2018

During the recent catastrophic heavy rainfall event in western Japan in July 2018, both the Hiroshima and Keihanshin areas were subjected to unusual total rainfall amounts in 72 hours from 1200 UTC 4 July to 1200 UTC 7 July. However, the number of sediment disasters was significantly larger in the Hiroshima area. We explore possible reasons for this difference in the sediment disaster occurrences between the Hiroshima and Keihanshin areas, focusing on the different rainfall characteristics in these two areas during the heavy rainfall event. Based on the radar observations, we investigate the characteristics of precipitation systems striking the Hiroshima and Keihanshin areas and find that significantly large precipitation systems, with areas equal to or larger than 104 km2, dominated the Hiroshima area, causing rapid accumulation of the rainfall amount and enhancing the risk of deadly sediment disasters in this area. On the other hand, in the Keihanshin area, moderately intense rainfall and relatively small precipitation systems were dominant. We suggest that the difference in the amount of damage between the Hiroshima and Keihanshin areas was mainly caused by the differently-sized precipitation systems striking these two areas. Statistics relating to the background atmospheric conditions for the precipitation systems in the heavy rainfall event reveal that a high vertical wind shear environment provides preferable conditions for the formation of large precipitation systems

The Effect of Water Vapor on Tropical Cyclone Genesis: A Numerical Experiment of a Non-Developing Disturbance Observed in PALAU2010

The environmental conditions for tropical cyclone genesis are examined by numerical experiment. We focus on the case of a non-developing disturbance showed features for tropical cyclone genesis in the Pacific Area Long-term Atmospheric observation for Understanding climate change in 2010 (PALAU2010) observation campaign over the western North Pacific. We clarify the importance of the presence of abundant moisture around the disturbance for continuous convection and demonstrate that the collocation of a mid-level vortex and a low-level vortex, i.e., the persistence of an upright structure of vortices, is important in tropical cyclone genesis. We conduct two numerical experiments using the Weather Research and Forecasting Model Advanced Research WRF model in double nested domains with a horizontal grid space of 27 km and 9 km for the outer domain and the inner domain, respectively. The first experiment is based on reanalysis data (a control experiment) and the second includes increased water vapor content over the northwestern dry area of the disturbance. In the control experiment, the disturbance did not develop into a tropical cyclone in spite of the existence of the mid-level and low-level vortices. In contrast, the sensitivity experiment shows that a tropical cyclone was formed from the disturbance with increased water vapor content. The presence of persistent upright vortices was supported by continuous convection until the genesis of the tropical cyclone