Citation network analysis is an effective tool to analyze the structure of scientific research. Clustering is often used to
visualize scientific domain and to detect emerging research front there. While we often set arbitrarily clustering threshold,
there is few guide to set appropriate threshold. This study analyzed basic process how clustering of citation network proceeds
by tracking size and modularity change during clustering. We found that there are three stages in clustering of citation networks
and it is universal across our case studies. In the first stage, core clusters in the domain are formed. In the second stage,
peripheral clusters are formed, while core clusters continue to grow. In the third stage, core clusters grow again. We found
the minimum corpus size around one hundred assuring the clustering. When the corpus size is less than one hundred, clustered
network structure tends to be more random. In addition even for the corpus whose size is larger than it, the clustering quality
for some clusters formed in the later stage is low. These results give a fundamental guidance to the user of citation network
Optics is an important research domain both for its scientific interest and industrial applications. In this paper, we constructed
a citation network of papers and performed topological clustering method to investigate the structure of research and to detect
emerging research domains in optics. We found that optics consists of main five subclusters, optical communication, quantum
optics, optical data processing, optical analysis and lasers. Then, we further investigated the detailed subcluster structures
in it. By doing so, we detected some emerging research domains such as nonlinearity in photonic crystal fiber, broad band
parametric amplifier, and in-vivo imaging techniques. We also discuss the distinction between research front and intellectual
base in optics.
Authors:Yoshiyuki Takeda, Shiho Mae, Yuya Kajikawa and Katsumori Matsushima
Nanotechnology has been intensively investigated by bibliometric methods due to its technological importance and expected
impacts on economic activity. However, there is less focus on nanobiotechnology, which is an emerging research domain in nanotechnology.
In this paper, we study the current status of the former, with our primary focus being to reveal the structure and research
domains in nanobiotechnology. We also examine country and institutional performance in nanobiotechnology. It emerged that
nanostructures, drug delivery and biomedical applications, bio-imaging, and carbon nanotubes and biosensors are the major
research domains, while the USA is the leading country, and China has also made substantial contribution. Most institutions
having a major impact in the area of nanobiotechnology are located in the USA.