Introducing my research
  I study about complex systems, not meaning that they are merely complicated. The complex system consists of a multitude of elements. They make interactions among themselves. It results in, throughout the system, the properties which could not be seen in discrete components. That is, we should not think of them as separate ones, and we can say that one plus one is no longer two. Looking at the system in this perspective, the unfound and hidden pattern and order can finally be discovered.
  The 2021 Nobel Prize in Physics was conferred to researchers who contributed to the complex system study. The media and public usually know that it was conferred to research about climate change, but the Nobel Foundation stated that it was a complex system. Specifically, it was an achievement that 1) made a theory about the random motion of disordered matters and 2) figured out the global climate and discovered the effect on the climate by humankind. It means that the prize was granted to two fields—the theoretical research toward the comprehension of the complex system and the applied research of climate change.
  It could be said that everything is a complex system. It, thereby, is utilized in diverse fields of research not only materials but also bio. Among them, I focus on the analysis of social data by means of complex systems and make an effort to understand the world.

  The motive for choosing this field
  I have enjoyed seeing the world of people since I was young. I thought the possession of substantial information was a competitive edge, and I was also interested in the computer. The amalgamation of all these things is my current research field.
  The researchable fields for us are expanding. This is by virtue of the development of computers retaining vast data and processing them. It makes me excited that the research fields I could make a contribution to in the future are inexhaustible.

  The approach of the complexity theory to our daily life
  It would be interesting to explain it using data which I usually handle. The complex research analyzing society initially focused on the Internet network. It is the paragon of complexity that countless computers have connected to one another. Since then, research has analyzed urban data like traffic, telecommunications, and roads, to broaden the scope.
  The complex system grasps the current system’s topology and nature and looks into the vulnerable parts of the system and resilience. For instance, the infection process is also modeled by a complex network structure. It was actively used during the pandemic of COVID-19.
  The data like a thesis, a patent, and industry help us see not only the progression of technologies and industries but also the related growth of cities, nations, and societies. Therefore, I endeavor to apply these analysis results to actual policies.

  Any impressive experiences in your research?
  As I mentioned earlier, I experienced several things while dealing with the application of the policy. What I learned a lot is, particularly, the optimization of the Seoul bus lines. The capital areas including Seoul have detailed subway-centric public traffic networks combined with bus lines. It is difficult to change the subway route once it is built. However, the bus could change its route more easily. A city is like a living creature. It is not developed into the preplanned. Accordingly, it is needed that an effort to construct a public transit system that is mostly suitable for citizens. The bus line is more likely to be changed, rather than the hard-changeable subway line. I was involved and came up with a solution to determine which route should be changed to operate the most efficient system in conjunction with the subway. As a result, I could not apply it on the site. I thought it was correct, but eventually, it was not. I succeeded in optimizing the public traffic network, but there are many other components that drive the traffic. For example, I did not consider one factor: revenue of the bus corporation. Furthermore, there would be more elements like bus drivers or buses in reserve. While I studied the complex system which considers system components and delves into their interactions and relationships, I did not approach it with the view of the complex system. People say nonscientific elements ought not to be involved in scientific stories. Thinking reversely, there are a lot of other things needed to operate society, not just science. Decision-making is a complex system; it needs deliberation about many other things beyond science. Internalizing what I learned then as a lesson, I made a conclusion that when I am supposed to render a policy-application to design a mathematical model with many more factors included.

  Advice for Postechians on how to understand complex systems and view society
  I think a complex system is close to an eye for the world, and paradigm, rather than a specific theory or academic field. However, there are errors that academics, especially those conducting convergence research, can easily fall into. The complex system is a field that originated in physics. In particular, it is based on statistical physics which looks into the system made of abundant parts. It is often said that in the eyes of a physicist, everything in the world looks like physics. By expanding the scope of natural phenomena that have been the subject of investigation by physicists, complexity theory even expands the world where people live into the field of inquiry of physics. What statistical physics pursues is ‘universality’, the property that could be found in a number of matters. It means it is about finding the universality of physics in other fields. The error occurs in this stage; it is impossible to demystify the social phenomena without the understanding of other fields. There is also a misconception that physics is superior to other disciplines and can replace all disciplines. Complexity is a representative field of interdisciplinary study. The starting point of interdisciplinary-convergent research lies in a deep degree of understanding about many studies and even other people, and high professionalism.